Squaric acid derivatives

ABSTRACT

Squaric acid derivatives of formula (1) are described:                    
     wherein 
     Het is an optionally substituted bicyclic fused ring heteroaromatic group; 
     L 2  is a covalent bond or an atom or group —O—, —S—, —C(O)—, —C(S)—, —S(O)—, —S(O) 2 , —N(R 8 )— or —C(R 8 )(R 8a )—; 
     Ar 2  is an optionally substituted aromatic or heteroaromatic group; 
     Alk is a chain                    
      in which R is a carboxylic acid (—CO 2 H) or a derivative or biostere thereof; 
     R 1  is a hydrogen atom or a C 1-6 alkyl group; 
     L 1  is a covalent bond or a linker atom or group; 
     Alk 1  is an optionally substituted aliphatic chain; 
     n is zero or the integer 1; 
     R 2  is a hydrogen atom or an optionally substituted heteroaliphatic, cycloaliphatic, heterocycloaliphatic, polycycloalphatic, heteropolycycloaliphatic, aromatic or heteroaromatic group other than a 2,6-naphthyridin-1-yl, isoquinolin-1-yl, 2,7-naphthyridin-1-yl or quinazolin-4-yl group; 
     and the salts, solvates, hydrates and N-oxides thereof. 
     The compounds are able to inhibit the binding of integrins to their ligands and are of use in the prophylaxis and treatment of immune or inflammatory disorders, or disorders involving the inappropriate growth or migration of cells.

This invention relates to a series of bicyclic heteroaromatic derivatives, to compositions containing them, to processes for their preparation, and to their use in medicine.

Over the last few years it has become increasingly clear that the physical interaction of inflammatory leukocytes with each other and other cells of the body plays an important role in regulating immune and inflammatory responses [Springer, T. A., Nature, 346, 425, (1990); Springer, T. A., Cell, 76, 301, (1994)]. Specific cell surface molecules collectively referred to as cell adhesion molecules mediate many of these interactions.

The adhesion molecules have been sub-divided into different groups on the basis of their structure. One family of adhesion molecules which is believed to play a particularly important role in regulating immune and inflammatory responses is the integrin family. This family of cell surface glycoproteins has a typical non-covalently linked heterodimer structure. At least 16 different integrin alpha chains and 8 different integrin beta chains have been identified [Newman, P. et al, Molecular Medicine Today, 304, (1996)]. The members of the family are typically named according to their heterodimer composition although trivial nomenclature is widespread in the field. Thus the integrin α4β1 consists of the integrin alpha 4 chain associated with the integrin beta 1 chain, but is also widely referred to as Very Late Antigen 4 or VLA-4. Not all of the potential pairings of integrin alpha and beta chains have yet been observed in nature and the integrin family has been subdivided into a number of subgroups based on the pairings that have been recognised to date [Sonnenberg, A., Current Topics in Microbiology and Immunology, 184, 7, (1993)].

The importance of integrin function in normal physiological responses is highlighted by two human deficiency diseases in which integrin function is defective. Thus in the disease termed Leukocyte Adhesion Deficiency (LAD) there is a defect in one of the families of integrins expressed on leukocytes [Marlin, S. D. et al, J. Exp. Med. 164, 855, (1986)]. Patients suffering from this disease have a reduced ability to recruit leukocytes to inflammatory sites and suffer recurrent infections, which in extreme cases may be fatal. In the case of patients suffering from the disease termed Glanzman's thrombasthenia (a defect in a member of the beta 3 integrin family) there is a defect in blood clotting (Hodivala-Dilke, K. M., J. Clin. Invest. 103, 229, (1999)].

The potential to modify integrin function in such a way as to beneficially modulate cell adhesion has been extensively investigated in animal models using specific antibodies and peptides that block various functions of these molecules [e.g. Issekutz, T. B., J. Immunol. 149, 3394, (1992); Li, Z. et al, Am. J. Physiol. 263, L723, (1992); Mitjans, F. et al, J. Cell Sci. 108, 2825, (1995); Brooks, P. C. et al, J. Clin. Invest. 96, 1815, (1995); Binns, R. M. etal, J. Immunol. 157, 4094, (1996); Hammes, H. -P. et al, Nature Medicine 2, 529, (1996); Srivata, S. et al, Cardiovascular Res. 36, 408 (1997)]. A number of monoclonal antibodies which block integrin function are currently being investigated for their therapeutic potential in human disease, and one, ReoPro, a chimeric antibody against the platelet integrin αIIbβ3 is in use as a potent anti-thrombotic agent for use in patients with cardiovascular complications following coronary angioplasty. Integrins recognize both cell surface and extracellular matrix ligands, and ligand specificity is determined by the particular alpha-beta subunit combination of the molecule [Newman, P., ibid]. One particular integrin subgroup of interest involves the α4 chain which can pair with two different beta chains β1 and β7 [Sonnenberg, A., ibid]. The α4β1 pairing occurs on many circulating leukocytes (for example lymphocytes, monocytes, eosinophils and basophils) although it is absent or only present at low levels on circulating neutrophils. α4β1 binds to an adhesion molecule (Vascular Cell Adhesion Molecule-1 also known as VCAM-1) frequently up-regulated on endothelial cells at sites of inflammation [Osborne, L., Cell, 62, 3, (1990)]. The molecule has also been shown to bind to at least three sites in the matrix molecule fibronectin [Humphries, M. J. et al, Ciba Foundation Symposium, 189, 177, (1995)]. Based on data obtained with monoclonal antibodies in animal models it is believed that the interaction between α4β1 and ligands on other cells and the extracellular matrix plays an important role in leukocyte migration and activation [Yednock, T. A. et al, Nature, 356, 63, (1992); Podolsky, D. K. et al, J. Clin. Invest. 92, 372, (1993); Abraham, W. M. et al, J. Clin. Invest. 93, 776, (1994)].

The integrin generated by the pairing of α4 and β7 has been termed LPAM-1 [Holzmann, B. and Weissman, I. L., EMBO J. 8, 1735, (1989)]. The α4β7 pairing is expressed on certain sub-populations of T and B lymphocytes and on eosinophils [Erie, D. J. et al, J. Immunol. 153, 517 (1994)]. Like α4β1, α4β7 binds to VCAM-1 and fibronectin. In addition, α4β7 binds to an adhesion molecule believed to be involved in the homing of leukocytes to mucosal tissue termed MAdCAM-1 [Berlin, C. et al, Cell, 74, 185, (1993)]. The interaction between α4β7 and MAdCAM-1 may also be important sites of inflammation outside of mucosal tissue [Yang, X. -D. et al, PNAS, 91,12604, (1994)].

Regions of the peptide sequence recognizeded by α4β1 and α4β7 when they bind to their ligands have been identified. α4β1 seems to recognise LDV, IDA or REDV peptide sequences in fibronectin and a QIDSP sequence in VCAM-1 [Humphries, M. J. et al, ibid] whilst α4β7 recognises a LDT sequence in MAdCAM-1 [Birskin, M. J. et al, J. Immunol. 156, 719, (1996)]. There have been several reports of inhibitors of these interactions being designed from modifications of these short peptide sequences [Cardarelli, P. M. et al, J. Biol. Chem., 269, 18668, (1994); Shorff, H. N. et al, Biorganic Med. Chem. Lett., 6, 2495, (1996); Vanderslice, P. et al, J. Immunol., 158, 1710, (1997)]. It has also been reported that a short peptide sequence derived from the α4β1 binding site in fibronectin can inhibit a contact hypersensitivity reaction in a trinitrochlorobenzene sensitised mouse [Ferguson, T. A., et al, PNAS, 88, 8072, (1991)].

Since the alpha 4 subgroup of integrins are predominantly expressed on leukocytes their inhibition can be expected to be beneficial in a number of immune or inflammatory disease states. However, because of the ubiquitous distribution and wide range of functions performed by other members of the integrin family it is important to be able to identify selective inhibitors of the alpha 4 subgroup.

We have now found a group of bicyclicheteroaromatic compounds which are potent and selective inhibitors of α4-integrins. Members of the group are able to inhibit α4 integrins such as α4β1 and α4β7 at concentrations at which they generally have no or minimal inhibitory action on α integrins of other subgroups. These compounds also possess good pharmacokinetic properties, especially low plasma clearance. The compounds are thus of use in medicine, for example in the prophylaxis and treatment of immune or inflammatory disorders as described hereinafter.

Thus according to one aspect of the invention we provide a compound of formula (1):

wherein

Het is a bicyclic fused ring heteroaromatic group;

g is zero or the integer 1, 2, 3 or 4;

Each R¹⁶, which may be the same or different is an atom or group —L³(Alk²)_(t)L⁴(R⁴)_(u) in which L³ and L⁴, which may be the same or different, is each a covalent bond or a linker atom or group, t is zero or the integer 1, u is an integer 1, 2 or 3, Alk² is an aliphatic or heteroaliphatic chain and R⁴ is a hydrogen or halogen atom or a group selected from optionally substituted C₁₋₆alkyl or C₃₋₈ cycloalkyl, —OR⁵ [where R⁵ is a hydrogen atom, an optionally substitued C₁₋₆alkyl or C₃₋₈ cycloalkyl group], —SR⁵, —NR⁵R⁶ [where R⁶ is as just defined for R⁵ and may be the same or different], —NO₂, —CN, —CO₂R⁵, —SO₃H, —SOR⁵, —SO₂R⁵, —SO₃R⁵, —OCO₂R⁵, —CONR⁵R⁶, —OCONR⁵R⁶, —CSNR⁵R⁶, —COR⁵, —N(R⁵)COR⁶, —N(R⁵)CSR⁶, —SO₂N(R⁵)(R⁶), —N(R⁵)SO₂R^(6 N(R) ⁵)CON(R⁶)(R⁷) [where R⁷ is a hydrogen atom, an optionally substituted C₁₋₆alkyl or C₃₋₈cycloalkyl group], —N(R⁵)CSN(R⁶)(R⁷) or —N(R⁵)SO₂N(R⁶)(R⁷), provided that when t is zero and each of L³ and L⁴ is a covalent bond then u is the integer 1 and R⁴ is other than a hydrogen atom;

L² is a covalent bond or an atom or group —O—, —S—, —C(O)—, —C(S)—, —S(O)—, —S(O)₂, —N(R⁸)— [where R⁸ is a hydrogen atom or an optionally substituted C₁₋₆alkyl group] or —C(R⁸)(R^(8a))— [where R^(8a) is an atom or group as defined for R⁸ and may be the same or different];

Ar² is an optionally substituted aromatic or heteroaromatic group;

Alk is a chain

 in which R is a carboxylic acid (—CO₂H) or a derivative or biostere thereof;

R¹ is a hydrogen atom or a C₁₋₆alkyl group;

L¹ is a covalent bond or a linker atom or group;

Alk¹ is an optionally substituted aliphatic chain;

n is zero or the integer 1;

R² is a hydrogen atom or an optionally substituted heteroaliphatic, cycloaliphatic, heterocycloaliphatic, polycycloalphatic, heteropolycycloaliphatic, aromatic or heteroaromatic group;

provided that Het is not a 2,6-naphthyridin-1-yl, isoquinolin-1-yl, 2,7-naphthyridin-1-yl or quinazolin-4-yl group;

and the salts, solvates, hydrates and N-oxides thereof.

It will be appreciated that compounds of formula (1) may have one or more chiral centres, and exist as enantiomers or diastereomers. The invention is to be understood to extend to all such enantiomers, diastereomers and mixtures thereof, including racemates. Formula (1) and the formulae hereinafter are intended to represent all individual isomers and mixtures thereof, unless stated or shown otherwise. In addition, compounds of formula (1) may exist as tautomers, for example keto(—CH₂C═O)-enol-(CHCHOH) tautomers. Formula (1) and the formulae hereinafter are intended to represent all individual tautomers and mixtures thereof, unless stated otherwise.

Bicyclic fused ring heteroaromatic groups represented by Het in the compounds of formula (1) include those bicyclic fused ring heteroaromatic groups containing a N heteroatom adjacent to the carbon atom that joins the Het group to the remainder of the compound of formula (1). Bicyclic heteroaromatic groups of this type include for example eight- to thirteen-membered fused-ring heteroaromatic groups containing one, two, three or more further heteroatoms selected from oxygen, sulphur or nitrogen atoms. Particular examples of heteroaromatic groups of this type include indol-2-yl, indazol-3-yl, benzoimidazol-2-yl, benzoxazol-2-yl, benzisoxazol-3-yl, benzthiazol-2-yl, purin-8-yl, purin-6-yl, purin-2-yl, quinolin-2-yl, cinnolin-3-yl, phthalazin-1-yl, quinoxalin-2-yl, pyrano[3,4-b]pyrrol-2-yl, pyrido[3,4-b]pyridin-2-yl, pyrido[3,4-b]pyridin-8-yl, pyrido[3,2-b]pyridin-2-yl, pyrido[4,3-b]pyridin-2-yl, pyrido[4,3-b]pyridin-5-yl, 1H-imidazo[4,5-b]pyrazin-2-yl, imidazo[1,5-a]pyridin-3-yl, 1H-imidazo[4,5-b]pyridin-2-yl, 1H-imidazo[4,5-c]pyridin-2-yl and pteridin-4-yl groups.

Further bicyclic fused ring heteroaromatic groups represented by Het in the compounds of formula (1) include groups of formula:

in which V and W is each independently selected from a nitrogen atom or a CH group, provided that both V and W are not nitrogen atoms, X, Y and Z is each independently selected from a nitrogen, oxygen or sulphur atom or CH group, X¹, Y¹ and Z¹ is each independently selected from a nitrogen atom or a CH group provided that when two of X¹, Y¹ and Z¹ are nitrogen atoms the other is a CH group, the broken line ( - - - ) represents saturation or unsaturation and the carbon atom identified by the letter b represents the point of attachment to the group L²Ar² in compounds of formula (1).

In bicyclic fused ring heteroaromatic groups represented by formula (1a) the partial ring structure:

includes for example optionally substituted rings selected from

In fused ring bicyclic heteroaromatic groups represented by formula (1a) the partial ring structure:

includes for example optionally substituted rings selected from:

In fused ring bicyclic heteroaromatic groups represented by formula (1b) the partial ring structure:

includes for example optionally substituted rings selected from:

Optional substituents which may be present on any available carbon atom of the bicyclic fused ring heteroaromatic groups represented by Het include those R¹⁶ atoms and groups as previously defined and as described hereinafter.

When L³ and/or L⁴ is present in the optional R¹⁶ substituents in compounds of formula (1) as a linker atom or group it may be any divalent linking atom or group. Particular examples include —O— or —S— atoms or —C(O)—, —C(O)O—, —OC(O)—, —C(S)—, —S(O)—, —S(O)₂—, —N(R⁸)— [where R⁸ is as previously defined], —N(R⁸)O—, —N(R⁸)N—, —CON(R⁸)—, —OC(O)N(R⁸)—, —CSN(R⁸)—, —N(R⁸)CO—, —N(R⁸)C(O)O—, —N(R⁸)CS—, —S(O)₂N(R⁸)—, —N(R⁸)S(O)₂—, —N(R⁸)CON(R⁸)—, —N(R⁸)CSN(R⁸)—, or —N(R⁸)SO₂N(R⁸)— groups. Where the linker group contains two R⁸ substituents, these may be the same or different.

When R⁴, R⁵, R⁶, R⁷ and/or R⁸ is present as a C₁₋₆alkyl group it may be a straight or branched C₁₋₆alkyl group, e.g. a C₁₋₃alkyl group such as a methyl, ethyl, propyl or 1-propyl group. C₃₋₈cycloalkyl groups represented by R⁴, R⁵, R⁶, R⁷ and/or R⁸ include C₃₋₆cycloalkyl groups e.g. cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl groups. Optional substituents which may be present on such groups include for example one, two or three substituents which may be the same or different selected from halogen atoms, for example fluorine, chlorine, bromine or iodine atoms, or hydroxy or C₁₋₆alkoxy e.g. methoxy or ethoxy groups.

When the groups R⁵ and R⁶ or R⁶ and R⁷ are both C₁₋₆alkyl groups these groups may be joined, together with the N atom to which they are attached, to form a heterocyclic ring. Such heterocyclic rings may be optionally interrupted by a further heteroatom selected from —O—, —S— or —N(R⁵)—. Particular examples of such heterocyclic rings include piperidinyl, morpholinyl, thiomorpholinyl, pyrrolidinyl, imidazolidinyl and piperazinyl rings.

When Alk² is present as an aliphatic or heteroaliphatic chain in the optional R¹⁶ substituents represented by —L³(Alk²)_(t)L⁴(R⁴)_(u) it may be for example any divalent chain corresponding to the below-mentioned aliphatic chains described for Alk¹ or heteroaliphatic groups described for R² in which one of the terminal hydrogen atoms is replaced by a bond.

Halogen atoms represented by R⁴ in the optional R¹⁶ substituents include fluorine, chlorine, bromine, or iodine atoms.

Examples of the substituents represented by —L³(Alk²)_(t)L⁴(R⁴)_(u) when present as R¹⁶ atoms or groups in compounds of the invention include atoms or groups —L³Alk²L⁴R⁴, —L³Alk²R⁴, —L³R⁴, —R⁴ and —Alk²R⁴ wherein L³, Alk², L⁴ and R⁴ are as defined above. Particular examples of such substituents include —L³CH₂L⁴R⁴, —L³CH(CH₃)L⁴R⁴, —L³CH(CH₂)₂L⁴R⁴, —L³CH₂R⁴, —L³CH(CH₃)R⁴, —L³(CH₂)₂R⁴, —CH₂R⁴, —CH(CH₃R⁴, —(CH₂)₂R⁴, and —R⁴ groups.

Thus the Het group in compounds of the invention may be optionally substituted for example by one, two, three or four R¹⁶ atoms or groups whee R¹⁶ may be a halogen atom, e.g. fluorine, chlorine, bromine or iodine atom, and/or C₁₋₆alkyl, e.g. methyl, ethyl, n-propyl, 1-propyl, n-butyl or t-butyl, C₃₋₈cycloalkyl, e.g. cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl, C₁₋₆hydroxyalkyl, e.g. hydroxymethyl, hydroxyethyl or —C(OH)(CF₃)₂, carboxyC₁₋₆alkyl, e.g. carboxyethyl, C₁₋₆alkylthio e.g. methylthio or ethylthio, carboxyC₁₋₆alkylthio, e.g. carboxymethylthio, 2-carboxyethylthio or 3-carboxypropylthio, C₁₋₆alkoxy, e.g. methoxy or ethoxy, hydroxyC₁₋₆alkoxy, e.g. 2-hydroxyethoxy, haloC₁₋₆alkyl, e.g. —CF₃ or —CHF₂, or —CH₂F, haloC₁₋₆alkoxy, e.g. —OCF₃, —OCHF₂ or —OCH₂F, C0 ₁₋₆alkylamino, e.g. methylamino or ethylamino, amino (—NH₂), aminoC₁₋₆alkyl, e.g. aminomethyl or aminoethyl, C₁₋₆dialkylamino, e.g. dimethylamino or diethylamino, C₁₋₆alkylaminoC₁₋₆alkyl, e.g. ethylamino-ethyl, C₁₋₆ dialkylaminoC₁₋₆alkyl, e.g. diethylaminoethyl, aminoC₁₋₆alkoxy, e.g. aminoethoxy, C₁₋₆alkylaminoC₁₋₆alkoxy, e.g. methylaminoethoxy, C₁₋₆dialkylaminoC₁₋₆alkoxy, e.g. dimethylaminoethoxy, diethylaminoethoxy, diisopropylaminoethoxy, or dimethylaminopropoxy, nitro, cyano, amidino, hydroxyl (—OH), formyl [HC(O)—], carboxyl (—CO₂H), —CO₂Alk³ [where Alk³ is as defined below for Alk⁷], C₁₋₆ alkanoyl e.g. acetyl, thiol (—SH), thioC₁₋₆alkyl, e.g. thiomethyl or thioethyl, sulphonyl (—SO₃H), —SO₃Alk³, C₁₋₆alkylsulphinyl, e.g. methylsulphinyl, C₁₋₆alkylsulphonyl, e.g. methylsulphonyl, aminosulphonyl (—SO₂NH₂), C₁₋₆ alkylaminosulphonyl, e.g. methylaminosulphonyl or ethylaminosulphonyl, C₁₋₆dialkylaminosulphonyl, e.g. dimethylaminosulphonyl or diethylaminosulphonyl, carboxamido (—CONH₂), C₁₋₆alkylaminocarbonyl, e.g. methylaminocarbonyl or ethylaminocarbonyl, C₁₋₆dialkylaminocarbonyl, e.g. dimethylaminocarbonyl or diethylaminocarbonyl, aminoC₁₋₆alkylaminocarbonyl, e.g. aminoethylaminocarbonyl, C₁₋₆dialkylaminoC₁₋₆alkylaminocarbonyl, e.g. diethylaminoethylaminocarbonyl, aminocarbonylamino, C₁₋₆alkylaminocarbonylamino, e.g. methylaminocarbonylamino or ethylaminocarbonylamino, C₁₋₆dialkylaminocarbonylamino, e.g. dimethylaminocarbonylamino or diethylaminocarbonylamino, C₁₋₆alkylaminocabonyl, C₁₋₆alkylamino, e.g. methylaminocarbonylmethylamino, aminothiocarbonylamino, C₁₋₆alkylaminothiocarbonylamino, e.g. methylaminothiocarbonylamino or ethylaminothiocarbonylamino, C₁₋₆dialkylaminothiocarbonylamino, e.g. dimethylaminothiocarbonylamino or diethylaminothiocarbonylamino, C₁₋₆alkylaminothiocarbonylC₁₋₆alkylamino, e.g. ethylaminothiocarbonylmethylamino, C₁₋₆alkylsulphonylamino, e.g. methylsulphonylamino or ethylsulphonylamino, C₁₋₆dialkylsulphonylamino, e.g. dimethylsulphonylamino or diethyl-sulphonylamino, aminosulphonylamino (—NHSO₂NH₂), C₁₋₆alkylaminosulphonylamino, e.g. methylaminosulphonylamino or ethylaminosulphonylamino, C₁₋₆dialkylaminosulphonylamino, e.g. dimethylaminosulphonylamino or diethylaminosulphonylamino, C₁₋₆alkanoylamino, e.g. acetylamino, aminoC₁₋₆alkanoylamino e.g. aminoacetylamino, C₁₋₆dialkylaminoC₁₋₆alkanoylamino, e.g. dimethylaminoacetylamino, C₁₋₆alkanoylaminoC₁₋₆alkyl, e.g. acetylaminomethyl, C₁₋₆alkanoylaminoC₁₋₆alkylamino, e.g. acetamidoethylamino, C₁₋₆alkoxycarbonylamino, e.g. methoxycarbonylamino, ethoxycarbonylamino or t-butoxycarbonylamino group.

Optionally substituted aromatic or heteroaromatic groups represented by Ar² include those aromatic or heteroaromatic groups described hereinafter in relation to R² aromatic or heteroaromatic groups respectively. The optional substituents which may be present on these groups include those optional substituents described in relation to R² aromatic or heteroaromatic groups.

When the group R is present in compounds of the invention as a derivative of a carboxylic acid it may be for example a carboxylic acid ester or amide. Particular esters and amides include —CO₂Alk⁷ and —CONR⁵R⁶ groups as defined herein. When R is a biostere of a carboxylic acid it may be for example a tetrazole or other acid such as phosphonic acid, phosphinic acid, sulphonic acid, sulphinic acid or boronic acid or an acylsulphonamide group.

Esters (—CO₂Alk⁷) and amide (—CONR⁵R⁶) derivatives of the carboxylic acid group (—CO₂H) in compounds of formula (1) may advantageously be used as prodrugs of the active compound. Such prodrugs are compounds which undergo biotransformation to the corresponding carboxylic acid prior to exhibiting their pharmacological effects and the invention particularly extends to prodrugs of the acids of formula (1). Such prodrugs are well known in the art, see for example International Patent Application No. WO00123419, Bodor, N. (Alfred Benzon Symposium, 1982, 17, 156-177), Singh, G. et al (J. Sci. Ind. Res., 1996, 55, 497-510) and Bundgaard, H., (Design of Prodrugs, 1985, Elsevier, Amsterdam.

Esterified carboxyl groups represented by the group —CO₂Alk⁷ include those wherein Alk⁷ is a straight or branched optionally substituted C₁₋₈alkyl group such as a methyl, ethyl, n-propyl, 1-propyl, n-butyl, 1-butyl, s-butyl or t-butyl group; an optionally substituted C₂₋₈alkenyl group such as a propenyl e.g. 2-propenyl or butenyl e.g. 2-butenyl or 3-butenyl group, an optionally substituted C₂₋₈alkynyl group such as a ethynyl, propynyl e.g. 2-propynyl or butynyl e.g. 2-butynyl or 3-butynyl group, an optionally substituted C₃₋₈cycloalkyl group such as a cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl group; an optionally substituted C₃₋₈cycloalkylC₁₋₈alkyl group such as a cyclopentylmethyl, cyclohexylmethyl or cyclohexylethyl group; an optionally substituted C₃₋₈heterocycloalkylC₁₋₆alkyl group such as a morpholinyl-N-ethyl, thiomorpholinyl-N-methyl, pyrrolidinyl-N-ethyl, pyrrolidinyl-N-propyl, piperidinyl-N-ethyl, pyrazolidinyl-N-methyl or piperazinyl-N-ethyl group; an optionally substituted C₁₋₆alkyloxyC₁₋₆alkyl group such as a methyloxyethyl or propyloxyethyl group; an optionally substituted C₁₋₆alkylthioC₁₋₆alkyl group such as an ethylthioethyl group; an optionally substituted C₁₋₆alkylsulfinylC₁₋₆alkyl group such as an methylsulfinylethyl group; an optionally substituted C₁₋₆alkylsulfonylC₁₋₆alkyl group such as an methylsulfonylmethyl group; an optionally substituted C₃₋₈cycloalkyloxyC₁₋₆alkyl group such as a cyclohexyloxymethyl group; an optionally substituted C₃₋₈cycloalkylthioC₁₋₆alkyl group such as a cyclopentylthiomethyl group; an optionally substituted C₃₋₈cycloalkylsulfinylC₁₋₆alkyl group such as a cyclopentylsulfinylmethyl group; an optionally substituted C₃₋₈cycloalkylsulfonylC₁₋₆alkyl group such as a cyclopentylsulfonylmethyl group; an optionally substituted C₁₋₆alkyloxycarbonylC₁₋₆alkyl group such as isobutoxycarbonylpropyl group; an optionally substituted C₁₋₆alkyloxycarbonylC₁₋₆alkenyl group such as isobutoxycarbonylpentenyl group; an optionally substituted C₁₋₆alkyloxy-carbonyloxyC₁₋₆alkyl group such as an isopropoxycarbonyloxyethyl e.g a 1-(isopropoxycarbonyloxy)ethyl, 2-(isopropoxycarbonyloxy)ethyl or ethyloxycarbonyloxymethyl group; an optionally substituted C₁₋₆alkyloxycarbonyloxyC₁₋₆alkenyl group such as a isopropoxycarbonyloxybutenyl group, an optionally substituted C₃₋₈cycloalkyloxycarbonyloxyC₁₋₆alkyl group such as a cyclohexyloxycarbonyloxyethyl, e.g. a 2-(cyclohexyloxycarbonyloxy)ethyl group, an optionally substituted N-di-C₁₋₈alkylaminoC₁₋₈alkyl group such as a N-dimethylaminoethyl or N-diethylaminoethyl group; an optionally substituted N—C₆₋₁₂aryl-N—C₁₋₁₆alkylaminoC₁₋₆alkyl group such as a N-phenyl-N-methylaminomethyl group; an optionally substituted N-di-C₁₋₈alkylcarbamoylC₁₋₈alkyl group such as a N-diethylcarbamoylmethyl group; an optionally substituted C₆₋₁₀arylC₁₋₆alkyl group such as an optionally substituted benzyl, phenylethyl, phenylpropyl, 1-naphthylmethyl or 2-naphthylmethyl group; a C₆₋₁₀aryl group such as an optionally substituted phenyl, 1-naphthyl or 2-naphthyl group; a C₆₋₁₀aryloxyC₁₋₈alkyl group such as an optionally substituted phenyloxymethyl, phenyloxyethyl, 1-naphthyloxymethyl, or 2-naphthyloxymethyl group; a C₆₋₁₂arylthioC₁₋₈alkyl group such as an optionally substituted phenylthioethyl group; a C₆₋₁₂arylsulfinylC₁₋₈alkyl group such as an optionally substituted phenylsulfinylmethyl group; a C₆₋₁₂arylsulfonylC₁₋₈alkyl group such as an optionally substituted phenylsulfonylmethyl group; an optionally substituted C₁₋₈alkanoyloxyC₁₋₈alkyl group, such as a acetoxymethyl, ethoxycarbonyloxyethyl, pivaloyloxymethyl, propionyloxyethyl or propionyloxypropyl group; an optionally substituted C₄₋₈imidoC₁₋₈alkyl group such as a succinimidomethyl or phthalamidoethyl group; a C₆₋₁₂aroyloxyC₁₋₈alkyl group such as an optionally substituted benzoyloxyethyl or benzoyloxypropyl group or a triglyceride such as a 2-substituted triglyceride e.g. a 1,3-di-C₁₋₁₈alkylglycerol-2-yl group such as a 1,3-diheptylglycerol-2-yl group. Optional substituents present on the Alk⁷ group include R^(13a) substituents described above.

It will be appreciated that in the forgoing list of Alk⁷ groups the point of attachment to the remainder of the compound of formula (1) is via the last described part of the Alk⁷ group. Thus, for example a methoxyethyl group would be attached by the ethyl group, whilst a morpholinyl-N-ethyl group would be attached via the N-ethyl group.

It will be further appreciated that in the forgoing list of Alk⁷ groups, where not specifically mentioned, alkyl groups may be replaced by alkenyl or alkynyl groups where such groups are as previously defined for the group Alk¹. Additionally these alkyl, alkenyl or alkynyl groups may optionally be interrupted by one, two or three linker atoms or groups where such linker atoms and groups are as previously defined for L³.

When the group R¹ is present in compounds of the invention as a C₁₋₆alkyl group it may be for example a straight or branched C₁₋₆alkyl group, e.g. a C₁₋₃alkyl group such as a methyl or ethyl group.

The linker atom or group represented by L¹ in compounds of formula (1) may be any linker atom or group as described above for the linker atom or group L³.

When the group Alk¹ is present in compounds of formula (1) as an optionally substituted aliphatic chain it may be an optionally substituted C₁₋₁₀ aliphatic chain. Particular examples include optionally substituted straight or branched chain C₁₋₆ alkylene, C₂₋₆ alkenylene, or C₂₋₆ alkynylene chains.

Particular examples of aliphatic chains represented by Alk¹ include optionally substituted —CH₂—, —(CH₂)₂—, —CH(CH₃)CH₂—, —(CH₂)₂CH₂—, —(CH₂)₃CH₂—, —CH(CH₃)(CH₂)₂—, —CH₂CH(CH₃)CH₂—, —C(CH₃CH₂, —CH₂C(CH₃)₂CH₂—, —(CH₂)₂C(CH₃)₂CH₂—, —(CH₂)₄CH₂—, —(CH₂)₅CH₂—, —CHCH—, —CHCHCH₂—, —CH₂CHCH—, —CHCHCH₂ CH₂—, —CH₂CHCHCH₂—, —(CH₂)₂CHCH—, —CC—, —CCCH₂—, —CH₂CC—, —CCCH₂CH₂—, —CH₂CCCH₂—, or —(CH₂)₂CCH— groups.

Heteroaliphatic groups represented by the group R² in the compounds of formula (1) include the aliphatic chains just described for Alk¹ but with each containing a further terminal hydrogen atom and additionally containing one, two, three or four heteroatoms or heteroatom-containing groups. Particular heteroatoms or groups include atoms or groups L⁵ where L⁵ is as defined above for L³ when L³ is a linker atom or group. Each L⁵ atom or group may interrupt the aliphatic group, or may be positioned at its terminal carbon atom to connect the group to an adjoining atom or group. Particular examples include optionally substituted —L⁵CH₃, —CH₂L⁵CH₃, —L⁵CH₂CH₃, —CH₂L⁵CH₂CH₃, —(CH₂)₂L⁵CH₃, —(CH₂)₃L⁵CH₃, —L⁵C(CH₃)₃, and —(CH₂)₂L⁵CH₂CH₃ groups.

The optional substituents which may be present on aliphatic chains or heteroaliphatic groups represented by Alk¹ and R² respectively include one, two, three or more substituents where each substituent may be the same or different and is selected from halogen atoms, e.g. fluorine, chlorine, bromine or iodine atoms, or —OH, —CO₂H, —CO₂R⁹, where R⁹ is an optionally substituted straight or branched C₁₋₆alkyl group or C₃₋₈cycloalkyl group as defined above for R⁴, —CONHR⁹, —CON(R⁹)₂, —COR⁹ e.g. —COCH₃, C₁₋₆alkoxy, e.g. methoxy or ethoxy, thiol, —S(O)R⁹, —S(O)₂R⁹, C₁₋₆alkylthio e.g. methylthio or ethylthio, amino or substituted amino groups. Substituted amino groups include —NHR⁹ and —N(R⁹)₂ groups. Where two R⁹ groups are present in any of the above substituents these may be the same or different.

Optionally substituted cycloaliphatic groups represented by the group R² in compounds of the invention include optionally substituted C₃₋₁₀ cycloaliphatic groups. Particular examples include optionally substituted C₃₋₁₀ cycloalkyl, e.g. C₃₋₇ cycloalkyl or C₃₋₁₀ cycloalkenyl, e.g C₃₋₇ cycloalkenyl groups.

Optionally substituted heterocycloaliphatic groups represented by the group R² include optionally substituted C₃₋₁₀heterocycloaliphatic groups. Particular examples include optionally substituted C₃₋₁₀heterocycloalkyl, e.g. C₃₋₇ heterocycloalkyl, or C₃₋₁₀heterocycloalkenyl, e.g. C₃₋₇ hetercycloalkenyl groups, each of said groups containing one, two, three or four heteroatoms or heteroatom-containing groups L⁵ as defined above.

Optionally substituted polycycloaliphatic groups represented by the group R² include optionally substitued C₇₋₁₀ bi- or tricycloalkyl or C₇₋₁₀bi- or tricycloalkenyl groups. Optionally substituted heteropolycycloaliphatic groups represented by the group R² include the optionally substituted polycycloalkyl groups just described, but with each group additionally containing one, two, three or four L⁵ atoms or groups.

Particular examples of cycloaliphatic, polycycloaliphatic, heterocycloaliphatic and heteropolycycloaliphatic groups represented by the group R² include optionally substituted cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, 2-cyclobuten-1-yl, 2-cyclopenten-1-yl, 3-cyclo-penten-1-yl, adamantyl, norbornyl, norbornenyl, tetrahydrofuranyl, pyrroline, e.g. 2- or 3-pyrrolinyl, pyrrolidinyl, pyrrolidinone, oxazolidinyl, oxazolidinone, dioxolanyl, e.g. 1,3-dioxolanyl, imidazolinyl, e.g. 2-imidazolinyl, imidazolidinyl, pyrazolinyl, e.g. 2-pyrazolinyl, pyrazolidinyl, pyranyl, e.g. 2- or 4-pyranyl, piperidinyl, homopiperidinyl, heptamethyleneiminyl, piperidinone, 1,4-dioxanyl, morpholinyl, morpholinone, 1,4-dithianyl, thiomorpholinyl, piperazinyl, homopiperazinyl, 1,3,5-trithianyl, oxazinyl, e.g. 2H-1,3-, 6H-1,3-, 6H-1,2-, 2H-1,2- or 4H-1,4-oxazinyl, 1,2,5-oxathiazinyl, isoxazinyl, e.g. o- or p-isoxazinyl, oxathiazinyl, e.g. 1,2,5 or 1,2,6-oxathiazinyl, or 1,3,5,-oxadiazinyl groups.

The optional substituents which may be present on the cycloaliphatic, polycycloaliphatic, heterocycloaliphatic or heteropolycycloaliphatic groups represented by the group R² include one, two, three or more substituents each selected from halogen atoms, e.g. fluorine, chlorine, bromine or iodine atoms, or C₁₋₆alkyl, e.g. methyl or ethyl, haloC₁₋₆alkyl, e.g. halomethyl or haloethyl such as difluoromethyl or trifluoromethyl, optionally substituted by hydroxyl, e.g. —C(OH)(CF₃)₂, C₁₋₆alkoxy, e.g. methoxy or ethoxy, haloC₁₋₆alkoxy, e.g. halomethoxy or haloethoxy such as difluoromethoxy or trifluoromethoxy, thiol, C₁₋₆alkylthio e.g. methylthio or ethylthio, or —(Alk⁴)_(v)R¹⁰ groups in which Alk⁴ is a straight or branched C₁₋₃alkylene chain, v is zero or an integer 1 and R¹⁰ is a —OH, —SH, —N(R¹¹)₂, (in which R¹¹ is an atom or group as defined herein for R⁸), —CN, —CO₂R¹¹, —NO₂, —CON(R¹¹)₂, —CSN(R¹¹)₂, —COR¹¹, —CSN(R¹¹)₂, —N(R¹¹)COR¹¹, —N(R¹¹)CSR¹¹, —SO₂N(R¹¹)₂, —N(R¹¹)SO₂R¹¹, —N(R¹¹)CON(R¹¹)₂, —N(R¹¹)CSN(R¹¹), —N(R¹¹)SO₂N(R¹¹)₂ or optionally substituted phenyl group. Where two R¹¹ atoms or groups are present in these substituents these may be the same or different. Additionally, when two R¹¹ groups are present as optionally substituted C₁₋₆alkyl groups these groups may be joined together with the atoms to which they are attached to form a heterocyclic ring. Such heterocyclic rings may be optionally interrupted by a further heteroatom selected from —O—, —S— or —N(R¹¹)—. Particular examples of such heterocyclic rings include piperidinyl, morpholinyl, thiomorpholinyl, pyrrolidinyl, imidazolidinyl and piperazinyl rings. Optionally substituted phenyl groups represented by R¹⁰ include phenyl substituted by one, two or three of the R¹³ groups described below.

Particular examples of Alk⁴ chains include —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂— and —CH(CH₃)CH₂— chains.

Additionally, when the group R² is a heterocycloaliphatic group containing one or more nitrogen atoms each nitrogen atom may be optionally substituted by a group —(L⁶)_(p)(Alk⁵)_(q)R¹² in which L⁶ is —C(O)—, —C(O)O—, —C(S)—, —S(O)₂—, —CON(R¹¹)—, —CSN(R¹¹)— or SO₂N(R¹¹)—; p is zero or an integer 1; Alk⁵ is an optionally substituted aliphatic or heteroaliphatic chain; q is zero or an integer 1; and R¹² is a hydrogen atom or an optionally substituted cycloaliphatic, heterocycloaliphatic, polycycloaliphatic, polyheterocycloaliphatic, aromatic or heteroaromatic group.

Optionally substituted aliphatic or heteroaliphatic chains represented by Alk⁵ include those optionally substituted chains described above for Alk¹ and R² respectively where in the case of R² a terminal hydrogen atom is replaced by a bond.

Cycloaliphatic, heterocycloaliphatic, polycycloaliphatic or heteropolycycloaliphatic groups represented by R¹² include those groups just described for the group R². Optional substituents which may be present on these groups include those described above in relation to Alk¹ aliphatic chains.

Aromatic and heteroaromatic groups represented by R¹² include those groups described hereinafter for the group R². Optional substituents which may be present on these groups include those described in relation to R² aromatic groups.

Optionally substituted aromatic groups represented by R² when present in the group R¹ include for example optionally substituted monocyclic or bicyclic fused ring C₆₋₁₂ aromatic groups, such as phenyl, 1- or 2-naphthyl, 1- or 2-tetrahydronaphthyl, indanyl or indenyl groups.

Optionally substituted heteroaromatic groups represented by the group R² include for example optionally substituted C₁₋₉ heteroaromatic groups containing for example one, two, three or four heteroatoms selected from oxygen, sulphur or nitrogen atoms. In general, the heteroaromatic groups may be for example monocyclic or bicyclic fused ring heteroaromatic groups. Monocyclic heteroaromatic groups include for example five- or six-membered heteroaromatic groups containing one, two, three or four heteroatoms selected from oxygen, sulphur or nitrogen atoms. Bicyclic heteroaromatic groups include for example eight- to thirteen-membered fused-ring heteroaromatic groups containing one, two or more heteroatoms selected from oxygen, sulphur or nitrogen atoms.

Particular examples of heteroaromatic groups of these types include pyrrolyl, furyl, thienyl, imidazolyl, N—C₁₋₆alkylimidazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyrazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl, 1,2,5-oxadiazolyl, 1,3,4-oxadiazolyl, 1,3,4-thiadiazole, pyridyl, pyrimidinyl, pyridazinyl, pyrazinyl, 1,3,5-triazinyl, 1,2,4-triazinyl, 1,2,3-triazinyl, benzofuryl, [2,3-dihydro]benzofuryl, [2,3-dihydro]benzothienyl, benzothienyl, benzotriazolyl, indolyl, isoindolyl, benzimidazolyl, imidazo[1,2-a]pyridyl, benzothiazolyl, benzoxazolyl, benzisoxazolyl, benzopyranyl, [3,4-dihydro]benzopyranyl, quinazolinyl, quinoxalinyl, naphthyridinyl, pyrido[3,4-b]pyridyl, pyrido[3,2-b]pyridyl, pyrido[4,3-b]pyridyl, quinolinyl, isoquinol inyl, tetrazolyl, 5,6,7,8-tetrahydroquinolinyl, 5,6,7,8-tetrahydroisoquinolinyl, and imidyl, e.g. succinimidyl, phthalimidyl, or naphthalimidyl such as 1,8-naphthalimidyl.

Optional substituents which may be present on the aromatic or heteroaromatic groups represented by the group R² include one, two, three or more substituents, each selected from an atom or group R¹³ in which R¹³ is —R^(13a) or —Alk⁶(R^(13a))_(m), where R^(13a) is a halogen atom, or an amino (—NH₂), substituted amino, nitro, cyano, amidino, hydroxyl (—OH), substituted hydroxyl, formyl, carboxyl (—CO₂H), esterified carboxyl, thiol (—SH), substituted thiol, —COR¹⁴ [where R¹⁴ is an —Alk⁶(R^(13a))_(m), cycloaliphatic, heterocycloaliphatic, aryl or heteroaryl group], —CSR¹⁴, —SO₃H, —SOR¹⁴, —SO₂R¹⁴, —SO₃R¹⁴, —SO₂NH₂, —SO₂NHR¹⁴, —SO₂N(R¹⁴)², —CONH₂, —CSNH₂, —CONHR¹⁴, —CSNHR¹⁴, —CON(R¹⁴)₂, —CSN(R¹⁴)₂, —N(R¹¹)SO₂R¹⁴, —N(SO₂R¹⁴)₂, —N(R¹¹)SO₂NH₂, —N(R¹¹)SO₂NHR¹⁴, —N(R¹¹)SO₂N(R¹⁴)₂, —N(R¹¹)COR¹⁴, —N(R¹¹)CONH₂, —N(R¹¹)CONHR¹⁴, —N(R¹¹)CON(R¹⁴)₂, —N(R¹¹)CSNH₂, —N(R¹¹)CSNHR¹⁴, —N(R¹¹)CSN(R¹⁴)₂, —N(R¹¹)CSR¹⁴, —N(R¹¹)C(O)OR¹⁴, —SO₂NHet¹ [where —NHet¹ is an optionally substituted C₅₋₇cyclicamino group optionally containing one or more other —O— or —S— atoms or —N(R¹¹)—, —C(O)—, —C(S)—, S(O) or —S(O)₂ groups], —CONHet¹, —CSNHet¹, —N(R¹¹)SO₂NHet¹, —N(R¹¹)CONHet¹, —N(R¹¹)CSNHet¹, —SO₂N(R¹¹)Het² [where Het² is an optionally substituted monocyclic C₅₋₇carbocyclic group optionally containing one or more —O— or —S— atoms or —N(R¹¹)—, —C(O)— or —C(S)— groups], —Het², —CON(R¹¹)Het², —CSN(R¹¹)Het², —N(R¹¹)CON(R¹¹)Het², —N(R¹¹)CSN(R¹¹)Het², cycloaliphatic, heterocycloaliphatic, aryl or heteroaryl group; Alk⁶ is a straight or branched C₁₋₆alkylene, C₂₋₆alkenylene or C₂₋₆alkynylene chain, optionally interrupted by one, two or three —O— or —S— atoms or —S(O)_(n) [where n is an integer 1 or 2] or —N(R¹⁵)— groups [where R¹⁵ is a hydrogen atom or C₁₋₆alkyl, e.g. methyl or ethyl group]; and m is zero or an integer 1, 2 or 3. It will be appreciated that when two R¹¹ or R¹⁴ groups are present in one of the above substituents, the R¹¹ or R¹⁴ groups may be the same or different.

When in the group —Alk⁶(R^(13a))_(m) m is an integer 1, 2 or 3, it is to be understood that the substituent or substituents R^(13a) may be present on any suitable carbon atom in —Alk⁶. Where more than one R^(13a) substituent is present these may be the same or different and may be present on the same or different atom in —Alk⁶. Clearly, when m is zero and no substituent R^(13a) is present the alkylene, alkenylene or alkynylene chain represented by Alk⁶ becomes an alkyl, alkenyl or alkynyl group.

When R^(13a) is a substituted amino group it may be for example a group —NHR¹⁴ [where R¹⁴ is as defined above] or a group —N(R¹⁴)₂ wherein each R¹⁴ group is the same or different.

When R^(13a) is a halogen atom it may be for example a fluorine, chlorine, bromine, or iodine atom.

When R^(13a) is a substituted hydroxyl or substituted thiol group it may be for example a group —OR¹⁴ or a —SR¹⁴ or —SC(═NH)NH₂ group respectively.

Esterified carboxyl groups represented by the group R^(13a) include groups of formula —CO₂Alk⁷, wherein Alk⁷ is a group as defined hereinbefore.

When Alk⁶ is present in or as a substituent it may be for example a methylene, ethylene, n-propylene, 1-propylene, n-butylene, 1-butylene, s-butylene, t-butylene, ethenylene, 2-propenylene, 2-butenylene, 3-butenylene, ethynylene, 2-propynylene, 2-butynylene or 3-butynylene chain, optionally interrupted by one, two, or three —O— or —S—, atoms or —S(O)—, —S(O)₂— or —N(R⁹)— groups.

Cycloaliphatic or heterocycloaliphatic groups represented by the groups R^(13a) or R¹⁴ include those optionally substituted C₃₋₁₀cycloaliphatic or C₃₋₁₀ heterocycloaliphatic groups described above for R².

Aryl or heteroaryl groups represented by the groups R^(13a) or R¹⁴ include mono- or bicyclic optionally substituted C₆₋₁₂ aromatic or C₁₋₉ heteroaromatic groups as described above for the group R². The aromatic and heteroaromatic groups may be attached to the remainder of the compound of formula (1) by any carbon or hetero e.g. nitrogen atom as appropriate.

When —NHet¹ or —Het² forms part of a substituent R¹³ each may be for example an optionally substituted pyrrolidinyl, pyrazolidinyl, piperazinyl, morpholinyl, thiomorpholinyl, piperidinyl or thiazolidinyl group. Additionally Het² may represent for example, an optionally substituted cyclopentyl or cyclohexyl group. Optional substituents which may be present on —NHet¹ or —Het² include those R⁷ substituents described above.

Particularly useful atoms or groups represented by R¹³ include fluorine, chlorine, bromine or iodine atoms, or C₁₋₆alkyl, e.g. methyl, ethyl, n-propyl, i-propyl, n-butyl or t-butyl, optionally substituted phenyl, pyridyl, pyrimidinyl, pyrrolyl, furyl, thiazolyl, thienyl, morpholinyl, thiomorpholinyl, piperazinyl, e.g. t-butyloxycarbonylpiperazinyl, pyrrolidinyl, dioxolanyl, dioxanyl, oxazolidinyl, thiazolidinyl, imidazolidinyl or piperidinyl, C₁₋₆hydroxyalkyl, e.g. hydroxymethyl or hydroxyethyl, carboxyC₁₋₆alkyl, e.g. carboxyethyl, C₁₋₆alkylthio e.g. methylthio or ethylthio, carboxyC₁₋₆alkylthio, e.g. carboxymethylthio, 2-carboxyethylthio or 3-carboxypropylthio, C₁₋₆alkoxy, e.g. methoxy or ethoxy, hydroxyC₁₋₆alkoxy, e.g. 2-hydroxyethoxy, optionally substituted phenoxy, pyridyloxy, thiazolyoxy, phenylthio or pyridylthio, C₄₋₇cycloalkyl, e.g. cyclobutyl, cyclopentyl, C₅₋₇cycloalkoxy, e.g. cyclopentyloxy, haloC₁₋₆alkyl, e.g. trifluoromethyl, haloC₁₋₆alkoxy, e.g. trifluoromethoxy, C₁₋₆alkylamino, e.g. methylamino, ethylamino or propylamino, C₆₋₁₂arylC₁₋₆alkylamino, e.g.benzylamino, 4-fluorobenzylamino or 4-hydroxyphenylethylamino, amino (—NH₂), aminoC₁₋₆alkyl, e.g. aminomethyl or aminoethyl, C₁₋₆dialkylamino, e.g. dimethylamino or diethylamino, aminoC₁₋₆alkylamino, e.g. aminoethylamino or aminopropylamino, optionally substituted Het¹NC₁₋₆alkylamino, e.g. 3-morpholinopropylamino, C₁₋₆alkylaminoC₁₋₆alkyl, e.g. ethylaminoethyl, C₁₋₆dialkylaminoC₁₋₆alkyl, e.g. diethylaminoethyl, aminoC₁₋₆alkoxy, e.g. aminoethoxy, C₁₋₆alkylaminoC₁₋₆alkoxy, e.g. methylaminoethoxy, C₁₋₆dialkylaminoC₁₋₆alkoxy, e.g. dimethylaminoethoxy, diethylaminoethoxy, diisopropylaminoethoxy, or dimethylaminopropoxy, hydroxyC₁₋₆alkylamino, e.g. 2-hydroxyethylamino, 3-hydroxypropylamino or 3-hydroxybutylamino, imido, such as phthalimido or naphthalimido, e.g. 1,8-naphthalimido, nitro, cyano, amidino, hydroxyl (—OH), formyl [HC(O)-], carboxyl (—CO₂H), —CO₂Alk⁷ [where Alk⁷ is as defined above], C₁₋₆ alkanoyl e.g. acetyl, propyryl or butyryl, optionally substituted benzoyl, thiol (—SH), thioC₁₋₆alkyl, e.g. thiomethyl or thioethyl, —SC(═NH)NH₂, sulphonyl (—SO₃H), —SO₃Alk⁷, C₁₋₆alkylsulphinyl, e.g. methylsulphinyl, ethylsulphinyl or propylsulphinyl, C₁₋₆alkylsulphonyl, e.g. methylsulphonyl, ethylsulphonyl or propylsulphonyl, aminosulphonyl (—SO₂NH₂), C₁₋₆alkylaminosulphonyl, e.g. methylaminosulphonyl, ethyl-aminosulphonyl or propylaminosulphonyl C₁₋₆dialkylaminosulphonyl, e.g. dimethylaminosulphonyl or diethylaminosulphonyl, phenylaminosulphonyl, carboxamido (—CONH₂), C₁₋₆alkylaminocarbonyl, e.g. methylaminocarbonyl, ethylaminocarbonyl or propylaminocarbonyl, C₁₋₆dialkylaminocarbonyl, e.g. dimethylaminocarbonyl or diethylaminocarbonyl, aminoC₁₋₆alkylaminocarbonyl, e.g. aminoethylaminocarbonyl, C₁₋₆alkylaminoC₁₋₆alkylaminocarbonyl, e.g. methylaminoethylaminocarbonyl, C₁₋₆dialkyl-aminoC₁₋₆alkylaminocarbonyl, e.g. diethylaminoethylaminocarbonyl, aminocarbonylamino, C₁₋₆alkylaminocarbonylamino, e.g. methylaminocarbonylamino or ethylaminocarbonylamino, C₁₋₆dialkylaminocarbonylamino, e.g. dimethylaminocarbonylamino or diethylaminocarbonylamino, C₁₋₆alkylaminocabonylC₁₋₆alkylamino, e.g. methylaminocarbonylmethylamino, aminothiocarbonylamino, C₁₋₆alkylaminothiocarbonylamino, e.g. methylaminothiocarbonylamino or ethylaminothiocarbonylamino, C₁₋₆dialkylaminothiocarbonylamino, e.g. dimethylaminothiocarbonylamino or diethylaminothiocarbonylamino, C₁₋₆alkylaminothiocarbonylC₁₋₆alkylamino, e.g. ethylaminothiocarbonylmethylamino, —CONHC(═NH)NH₂, C₁₋₆alkylsulphonylamino, e.g. methylsulphonylamino or ethylsulphonylamino, haloC₁₋₆alkylsulphonylamino, e.g. trifluoromethylsulphonylamino, C₁₋₆ dialkylsulphonylamino, e.g. dimethylsulphonylamino or diethylsulphonylamino, optionally substituted phenylsulphonylamino, aminosulphonylamino (—NHSO₂NH₂), C₁₋₆alkylaminosulphonylamino, e.g. methylaminosulphonylamino or ethylaminosulphonylamino, C₁₋₆dialkylaminosulphonylamino, e.g. dimethylaminosulphonylamino or diethylaminosulphonylamino, optionally substituted morpholinesulphonylamino or morpholinesulphonylC₁₋₆alkylamino, optionally substituted phenylaminosulphonylamino, C₁₋₆alkanoylamino, e.g. acetylamino, aminoC₁₋₆alkanoylamino e.g. aminoacetylamino, C₁₋₆dialkylaminoC₁₋₆alkanoylamino, e.g. dimethylaminoacetylamino, C₁₋₆alkanoylaminoC₁₋₆alkyl, e.g. acetylaminomethyl, C₁₋₆alkanoylaminoC₁₋₆alkylamino, e.g. acetamidoethylamino, C₁₋₆alkoxycarbonylamino, e.g. methoxycarbonylamino, ethoxycarbonylamino or t-butoxycarbonylamino or optionally substituted benzyloxy, pyridylmethoxy, thiazolylmethoxy, benzyloxycarbonylamino, benzyloxycarbonylaminoC₁₋₆alkyl e.g. benzyloxycarbonylaminoethyl, thiobenzyl, pyridylmethylthio or thiazolylmethylthio groups.

Where desired, two R¹³ substituents may be linked together to form a cyclic group such as a cyclic ether, e.g. a C₁₋₆alkylenedioxy group such as methylenedioxy or ethylenedioxy.

It will be appreciated that where two or more R¹³ substituents are present, these need not necessarily be the same atoms and/or groups. In general, the substituent(s) may be present at any available ring position in the aromatic or heteroaromatic group represented by R².

The presence of certain substituents in the compounds of formula (1) may enable salts of the compounds to be formed. Suitable salts include pharmaceutically acceptable salts, for example acid addition salts derived from inorganic or organic acids, and salts derived from inorganic and organic bases.

Acid addition salts include hydrochlorides, hydrobromides, hydroiodides, alkylsulphonates, e.g. methanesulphonates, ethanesulphonates, or isothionates, arylsulphonates, e.g. p-toluenesulphonates, besylates or napsylates, phosphates, sulphates, hydrogen sulphates, acetates, trifluoroacetates, propionates, citrates, maleates, fumarates, malonates, succinates, lactates, oxalates, tartrates and benzoates.

Salts derived from inorganic or organic bases include alkali metal salts such as sodium or potassium salts, alkaline earth metal salts such as magnesium or calcium salts, and organic amine salts such as morpholine, piperidine, dimethylamine or diethylamine salts.

Particularly useful salts of compounds according to the invention include pharmaceutically acceptable salts, especially acid addition pharmaceutically acceptable salts.

A particularly useful group of compounds according to the invention has the formula (2a):

wherein R¹⁷ is an atom or group R¹⁶ as previously generally and particularly defined, h is the integer g-1 where g is the integer 1, 2, 3 or 4 and R¹⁸ is a hydrogen atom or an atom or group R¹⁶; L¹, L², Ar², Alk, R¹, n and R² are as defined for formula (1); and the salts, solvates, hydrates and N-oxides thereof.

Particularly useful R¹⁷ substituents when present in compounds of formula (2a) include halogen atoms, especially fluorine or chlorine atoms, or straight or branched C₁₋₆alkyl especially methyl, ethyl, propyl or isopropyl, haloC₁₋₆alkyl especially halomethyl, most especially —CF₃ or —CHF₂ C₁₋₆alkoxy especially methoxy or ethoxy, haloC₁₋₆alkoxy especially halomethoxy, most especially —OCF₃, or —OCHF₂, —SR⁵ especially methylthio or ethylthio, —CN, —CO₂Alk³, especially —CO₂CH₃, —NO₂, amino (—NH₂), substituted amino (—NR⁵R⁶), especially —N(CH₃)₂, —N(R⁵)COCH₃, especially —NHCOCH₃ and —COR⁵, especially —COCH₃ groups.

In one preferred class of compounds of formula (2a) h is zero.

In another preferred class of compounds of formula (2a) h is the integer 1 or 2 and each R¹⁷ is independently chosen from a hydrogen, fluorine or chlorine atom or a C₁₋₆alkyl especially methyl or ethyl, —N(CH₃)₂, —CN, —CF₃, methoxy or —OCF₃ group.

In another preferred class of compounds of formula (2a) R¹⁸ is a hydrogen atom.

In another preferred class of compounds of formula (2a) R¹⁸ is a straight or branched C₁₋₆alkyl group, especially a methyl, ethyl, propyl or isopropyl group.

Another particularly useful group of compounds according to the invention has the formula (2b):

wherein R¹⁶ is a hydrogen atom or an atom or group —L³(Alk²)_(t)L⁴(R⁴)_(u) in which L³, Alk², t, L⁴, R⁴, and u are as previously generally and particularly defined;

X, Y, Z, the broken line ( - - - ), g, L¹, L², Ar², Alk, R¹, Alk¹, n and R² are as defined previously;

and the salts, solvates, hydrates and N-oxides thereof.

In one preferred class of compounds of formulae (1) and (2b) X is an O or S atom and Y and Z are each a CH group, a single bond joins X and Y and a double bond joins Y and Z.

In another preferred class of compounds of formulae (1) and (2b) Z is an O or S atom and X and Y are each a CH group, a single bond joins Y and Z and a double bond joins X and Y.

Particularly useful R¹⁶ substituents when present in compounds of formula (2) include halogen atoms, especially fluorine or chlorine atoms, or straight or branched C₁₋₆alkyl especially methyl, ethyl, propyl or isopropyl, C₃₋₈cycloalkyl especially cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl, haloC₁₋₆alkyl especially halomethyl, most especially —CF₃ or —CHF₂ C₁₋₆alkoxy especially methoxy or ethoxy, haloC₁₋₆alkoxy especially halomethoxy, most especially —OCF₃, or —OCHF₂, —SR⁵ especially methylthio or ethylthio, —CN, —CO₂Alk³, especially —CO₂CH₃, —NO₂, amino (—NH₂), substituted amino (—NR⁵R⁶), and —N(R⁵)COCH₃, especially —NHCOCH₃ and —COR⁵, especially —COCH₃ groups.

Alk in compounds of the invention is preferably:

 or; especially, —CH₂CH(R)—.

In one prefered class of compounds of formulae (1), (2a) and (2b) R is a —CO₂H group.

In another prefered class of compounds of formulae (1), (2a) and (2b) R is an esterified carboxyl group of formula —CO₂Alk⁷. In this class of compound Alk⁷ is preferably a C₁₋₈alkyl group, especially a methyl, ethyl, propyl or 1-propyl group, an optionally substituted C₆₋₁₀aryl group, especially a phenyl group, an optionally substituted C₆₋₁₀arylC₁₋₆alkyl group, especially a benzyl group, a C₃₋₈heterocycloalkylC₁₋₆alkyl group, especially a morpholinyl-N-ethyl group or a C₁₋₆alkyloxyC₁₋₆alkyl group, especially a methyloxyethyl group. Especially preferred esterified carboxyl groups include —CO₂CH₂CH₃, —CO₂CH₂CH₂CH₃ and —CO₂CH(CH₃)₂ groups.

In general in compounds of formulae (1), (2a) and (2b) R¹ is preferably a hydrogen atom.

In general in compounds of formulae (1), (2a) and (2b) L² is preferably a −O— atom or —N(R⁸)— group. Especially useful —N(R⁸)— groups include —NH— and —N(CH₃)—, most especially —NH—.

The group Ar² in compounds of formulae (1), (2a) and (2b) is preferably an optionally substituted phenylene group. Particularly useful groups include optionally substituted 1,4-phenylene groups.

In general in compounds of formulae (1) and (2) when n is zero or the integer 1 the group R² may especially be an optionally substituted heteroaliphatic, cycloaliphatic, heterocycloaliphatic, aromatic or heteroaromatic group as defined herein. Particularly useful groups of this type include optionally substituted C₂₋₆heteroalkyl, particularly C₁₋₃alkoxyC₁₋₃alkyl, especially methoxypropyl, optionally substituted C₃₋₇cycloalkyl, especially optionally substituted cyclopropyl, cyclobutyl cyclopentyl or cyclohexyl, optionally substituted C₅₋₇heterocycloaliphatic, especially optionally substituted pyrrolidinyl, morpholinyl, thiomorpholinyl, or thiazolidinyl, especially optionally substituted phenyl and optionally substituted C₅₋₇heteroaromatic, especially optionally substituted pyridyl and pyrimidinyl groups. Optional substituents on these groups include in particular R¹³ atoms or groups where the group is an aromatic or heteroaromatic group and —(L⁶)_(p)(Alk⁵)_(q)R¹² groups as described earlier where the group is a nitrogen-containing heterocycloaliphatic group such as a pyrrolidinyl or thiazolidinyl group. Particularly useful —(L⁶)_(p)(Alk⁵)_(q)R¹² groups include those in which L⁶ is a —CO— group. Alk⁵ in these groups is preferably present (i.e. q is preferably an integer 1) and in particular is a —CH₂ chain. Compounds of this type in which R¹² is a hydrogen atom or an optionally substituted aromatic or heteroaromatic group, especially an optionally substituted phenyl, pyridyl or imidazolyl group are particularly preferred.

In one preferred class of compounds of formulae (1) and (2) L¹ is present as a —N(R⁸)— group. Particularly useful —N(R⁸)— groups include —NH—, —N(CH₃)—, —N(CH₂CH₃)— and —N(CH₂CH₂CH₃)— groups. In this class of compounds n is preferably the integer 1 and Alk¹ is preferably an optionally substituted straight or branched C₁₋₆alkylene chain. Particularly useful Alk¹ chains include —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂— and —C(CH₃)₂CH₂—. R² in this class of compounds is preferably a hydrogen atom.

In another preferred class of compounds of formulae (1) and (2) L¹ is a covalent bond, n is the integer (1) and Alk¹ is an optionally substituted straight or branched C₁₋₆alkylene chain. Particularly useful Alk¹ chains include —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂— and especially —C(CH₃)₂CH₂— chains. R² in this class of compounds is preferably a hydrogen atom. A most especially useful optionally substituted Alk¹R² group is —C(CH₃)₃.

In another preferred class of compounds of formulae (1) and (2), L¹ is a covalent bond, n is zero and R² is an optionally substituted C₅₋₇heterocycloaliphatic group. Especially useful C₅₋₇heterocycloaliphatic groups include optionally substituted piperidinyl, homopiperidinyl, heptamethyleneiminyl, pyrrolidinyl, piperazinyl, homopiperazinyl, morpholinyl and thiomorpholinyl groups. Most preferred C₅₋₇heterocycloaliphatic groups are those linked via a ring nitrogen atom to the remainder of the compound of formulae (1) or (2). Most especially useful C₅₋₇ heterocycloaliphatic groups include optionally substituted pyrolidin-1-yl, piperidin-1-yl and homopiperidin-1-yl groups. Especially useful optional substituents on these C₅₋₇heterocycloaliphatic groups include optionally substituted C₁₋₆alkyl groups, especially methyl, ethyl and 1-propyl groups. Most preferred optionally substitued C₅₋₇heterocycloaliphatic groups include 2-methylpyrrolidin-1-yl, cis and trans 2,5-dimethylpyrrolidin-1-yl, 2-methylpiperidin-1-yl, cis and trans 2,6-dimethylpiperidin-1-yl, homopiperidin-1-yl, 2-methylhomopiperidin-1-yl and cis and trans 2,7-dimethylhomopiperidin-1-yl groups.

Particularly useful compounds of the invention include:

S-2-{[2-Dipropylamino)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid;

S-2-{[2-Dipropylamino)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid;

S-2-{[2-(2-Methylpiperidin-1-yl)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid;

(S)-3-[4-(Thiephen[2,3-d]pyrimidin-4-ylamino)phenyl]2-(2-(diethylamino-3,4-dioxocyclobut-1-enylamino)propanoic acid;

and the salts, solvates, hydrates, N-oxides and carboxylic acid esters, particularly the methyl, ethyl, propyl and 1-propyl esters thereof.

Compounds according to the inventions are potent and selective inhibitors of α4 integrins and have advantageous clearance properties, especially those copounds where R is a carboxylic acid ester or amide. The ability of the compounds to act in this way may be simply determined by employing tests such as those described in the Examples hereinafter.

The compounds are of use in modulating cell adhesion and in particular are of use in the prophylaxis and treatment of diseases or disorders involving inflammation in which the extravasation of leukocytes plays a role and the invention extends to such a use and to the use of the compounds for the manufacture of a medicament for treating such diseases or disorders.

Diseases or disorders of this type include inflammatory arthritis such as rheumatoid arthritis vasculitis or polydermatomyositis, multiple sclerosis, allograft rejection, diabetes, inflammatory dermatoses such as psoriasis or dermatitis, asthma and inflammatory bowel disease.

For the prophylaxis or treatment of disease the compounds according to the invention may be administered as pharmaceutical compositions, and according to a further aspect of the invention we provide a pharmaceutical composition which comprises a compound of formula (1) together with one or more pharmaceutically acceptable carriers, excipients or diluents.

Pharmaceutical compositions according to the invention may take a form suitable for oral, buccal, parenteral, nasal, topical or rectal administration, or a form suitable for administration by inhalation or insufflation.

For oral administration, the pharmaceutical compositions may take the form of, for example, tablets, lozenges or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (e.g. lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (e.g. magnesium stearate, talc or silica); disintegrants (e.g. potato starch or sodium glycollate); or wetting agents (e.g. sodium lauryl sulphate). The tablets may be coated by methods well known in the art. Liquid preparations for oral administration may take the form of, for example, solutions, syrups or suspensions, or they may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents, emulsifying agents, non-aqueous vehicles and preservatives. The preparations may also contain buffer salts, flavouring, colouring and sweetening agents as appropriate.

Preparations for oral administration may be suitably formulated to give controlled release of the active compound.

For buccal administration the compositions may take the form of tablets or lozenges formulated in conventional manner.

The compounds for formula (1) may be formulated for parenteral administration by injection e.g. by bolus injection or infusion. Formulations for injection may be presented in unit dosage form, e.g. in glass ampoule or multi dose containers, e.g. glass vials. The compositions for injection may take such forms as suspensions, solutions or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising, preserving and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle, e.g. sterile pyrogen-free water, before use. For particle mediated administration the compounds of formula (1) may be coated on particles such as microscopic gold particles.

In addition to the formulations described above, the compounds of formula (1) may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation or by intramuscular injection.

For nasal administration or administration by inhalation, the compounds for use according to the present invention are conveniently delivered in the form of an aerosol spray presentation for pressurised packs or a nebuliser, with the use of suitable propellant, e.g. dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas or mixture of gases.

For vaginal or rectal administration the compounds of formula (1) may be formulated as a suppository. These formulations may be prepared by mixing the active ingredient with a suitable non-irritating excipient which is a solid at room temperature but liquid at the body temperature. Such materials include for example cocoa butter and polyethylene glycols.

The compositions may, if desired, be presented in a pack or dispenser device which may contain one or more unit dosage forms containing the active ingredient. The pack or dispensing device may be accompanied by instructions for administration.

The quantity of a compound of the invention required for the prophylaxis or treatment of a particular condition will vary depending on the compound chosen, and the condition of the patient to be treated. In general, however, daily dosages may range from around 100 ng/kg to 100 mg/kg e.g. around 0.01 mg/kg to 40 mg/kg body weight for oral or buccal administration, from around 10 ng/kg to 50 mg/kg body weight for parenteral administration and around 0.05 mg to around 1000 mg e.g. around 0.5 mg to around 1000 mg for nasal administration or administration by inhalation or insufflation.

The compounds of the invention may be prepared by a number of processes as generally described below and more specifically in the Examples hereinafter. In the following process description, the symbols Ar², Alk, R¹, R², L¹, L², Alk¹ and n when used in the formulae depicted are to be understood to represent those groups described above in relation to formula (1) unless otherwise indicated. In the reactions described below, it may be necessary to protect reactive functional groups, for example hydroxy, amino, thio or carboxy groups, where these are desired in the final product, to avoid their unwanted participation in the reactions. Conventional protecting groups may be used in accordance with standard practice [see, for example, Green, T. W. in “Protective Groups in Organic Synthesis”, John Wiley and Sons, 1991]. In some instances, deprotection may be the final step in the synthesis of a compound of formula (1) and the processes according to the invention described hereinafter are to be understood to extend to such removal of protecting groups. For convenience the processes described below all refer to a preparation of a compound of formula (1) but clearly the description applies equally to the preparation of compounds of formula (2).

Thus according to a further aspect of the invention, a compound of formula (1) in which R is a —CO₂H group may be obtained by hydrolysis of an ester of formula (3):

where Ar¹ represents a bicyclic fused-ring heteroaromatic group as previously generally and particularly described;

and Alk represents a group

[where R^(y) is an alkyl group for example a C₁₋₆alkyl group]

The hydrolysis may be performed using either an acid or a base depending on the nature of R^(y), for example an organic acid such as trifluoroacetic acid or an inorganic base such as lithium, sodium or potassium hydroxide optionally in an aqueous organic solvent such as an amide e.g. a substituted amide such as dimethylformamide, an ether e.g. a cyclic ether such as tetrahydrofuran or dioxane or an alcohol e.g. methanol at a temperature from ambient to the reflux temperature. Where desired, mixtures of such solvents may be used.

According to a further aspect of the invention a compound of formula (1) may be prepared by displacement of a leaving group from a compound of formula (4):

where R^(a) is a leaving group, with an amine Ar¹L²Ar²AlkN(R¹)H or a salt thereof. Suitable leaving groups represented by R^(a) include halogen atoms, especially chlorine and bromine atoms, or alkoxy, e.g. methoxy, ethoxy or isopropoxy, aryloxy, e.g. dinitrophenyloxy, or aralkoxy, e.g. benzyloxy, groups.

The reaction may be performed in an inert solvent or mixture of solvents, for example a substituted amide such as dimethylformamide, an alcohol such as ethanol and/or a halogenated hydrocarbon such as dichloromethane, at a temperature from 0° C. to the reflux temperature. Where necessary, for example when a salt of an amine Ar¹L²Ar²AlkN(R¹)H is used, an organic base such as diisopropylethylamine can be added.

Any carboxylic acid group present in the intermediate of formula (4) or the amine Ar¹L²Ar²AlkN(R¹)H may need to be protected during the displacement reaction, for example as an ethyl ester. The desired acid may then be obtained through subsequent hydrolysis, for example as particularly described above and generally described below.

It will be appreciated that the displacement reaction may also be performed on a compound of formula (5):

where R^(b) is a leaving group as defined for R^(a) using an intermediate R²(Alk¹)_(n)L¹H where —L¹H is a functional group such as an amine (—NH₂) using the reaction conditions just described.

It will be further appreciated that when L¹ is a covalent bond the displacement reaction may be performed on a compound of formula (5) using an organometallic intermediate of formula R²(Alk¹)_(n)M [where M represents a metal such as Li or MgHal, where Hal is a halogen atom such as a chlorine, bromine or iodine atom].

The reaction may be performed in an inert solvent such as an ether e.g. a cyclic ether such as tetrahydrofuran at a temperature from about −78° C. to ambient temperature.

Where desired the displacement reaction may also be performed on an intermediate of formulae (4) or (5), Ar¹L²Ar²AlkN(R¹)H or R²(Alk¹)_(n)L¹H which is linked, for example via its Ar¹ or R² group, to a solid support, such as a polystyrene resin. After the reaction the desired compound of formula (1) may be displaced from the support by any convenient method, depending on the original linkage chosen.

Intermediates of formulae (4) and (5) are either readily available or may be prepared from an intermediate of formula (6):

where R^(a) and R^(b) are as previously defined and an amine Ar¹L²Ar²AlkN(R¹)H or R²(Alk¹)_(n)L¹H or organometallic R²(Alk¹)_(n)M by displacement as just described for the preparation of compounds of formula (1).

Intermediates of formulae Ar¹L²Ar²AlkN(R¹)H, R²(Alk¹)_(n)L¹H and R²(Alk¹)_(n)M may be obtained from simpler, known compounds by one or more standard synthetic methods employing substitution, oxidation, reduction or cleavage reactions. Particular substitution approaches include conventional alkylation, arylation, heteroarylation, acylation, thioacylation, halogenation, sulphonylation, nitration, formylation and coupling procedures. It will be appreciated that these methods may also be used to obtain or modify other compounds of formulae (1) and (2) where appropriate functional groups exist in these compounds. Thus such intermediates may be prepared by methods known to those skilled in the art following procedures set forth in such references as Rodd's Chemisty of Carbon Compounds, Volumes 1-15 and Supplementals (Elsevier Science Publishers, 1989); Fieser and Fieser's Reagents for Organic Synethesis, Voumes 1-19 (John Wiley & Sons, 1999); Comprehensive Heterocyclic Chemistry, Ed. Kartitzky et al, Volumes 1-8, 1984 and Volumes 1-11, 1994 (Pergamon); Comprehensive Organic Functional Group Transformations, Ed. Trost & Flemming, Volumes 1-8, (Pergamon, 1991); Encyclopedia of Reagents for Organic Synethesis Ed. Paquette, Volumes 1-9 (John Wiley & Sons, 1995); Larock's Comprehensive Organic Transformations (VCH Publishers Inc., 1989) and March's Advanced Organic Chemistry (John Wiley & Sons, 1992).

Thus compounds of the invention and intermediates thereto may be prepared by alkylation, arylation or heteroarylation. For example, compounds containing a —L¹H or —L²H group (where L¹ and L² is each a linker atom or group) may be treated with a coupling agent R²(Alk¹)_(n)X¹ or Ar¹X¹ respectively in which X¹ is a leaving atom or group such as a halogen atom, e.g. a fluorine, bromine, iodine or chlorine atom or a sulphonyloxy group such as an alkylsulphonyloxy, e.g. trifluoromethylsulphonyloxy or arylsulphonyloxy, e.g. p-toluene-sulphonyloxy group.

The reaction may be carried out in the presence of a base such as a carbonate, e.g. caesium or potassium carbonate, an alkoxide, e.g. potassium t-butoxide, or a hydride, e.g. sodium hydride, or an organic amine e.g. triethylamine or N,N-diisopropylethylamine or a cyclic amine, such as N-methylmorpholine or pyridine, in a dipolar aprotic solvent such as an amide, e.g. a substituted amide such as dimethylformamide or an ether, e.g. a cyclic ether such as tetrahydrofuran.

Intermediates of formulae Ar¹X¹ and R²(Alk¹)_(n)X¹ are generally known readily available compounds or may be prepared from known compounds by standard substitution and other synthetic procedures, for example as described herein. Thus for example compounds of formula Ar¹ X¹ in which may be prepared from alcohols of formula Ar¹ OH (or their ketotauomers) by reaction with a halogenating agent, for example a phosphorous oxyhalide such as phosphorous oxychloride or thionyl chloride optionally or an inert solvent such as an amide e.g. a substituted amide such as dimethylformamide or a sulfonic acid e.g. methane sulfonic acid at an elevated temperature e.g. 110° C.

In a further example intermediates of formula Ar¹L²Ar²AlkN(R¹)H may be obtained by reaction of a compound of formula Ar¹L²H with a compound of formula X¹Ar²AlkN(R¹)H under the reaction conditions just described

Compounds of formula Ar¹L²H in which, L² is a —N(R⁸)— group, may be prepared from compounds of formula Ar¹Hal [where Hal is a halogen atom such as a chlorine or bromine atom] by treatment with an amine, (R⁸)NH₂, optionally in the presence of a base such as an inorganic base for example a carbonate e.g. potassium or caesium carbonate or an organic base such as an amine e.g. triethylamine or N-methylmorpholine in an inert solvent such as an amide e.g. a substituted amide such as dimethylformamide or an ether e.g. a cyclic ether such as tetrahydrofuran or a halogenated hydrocarbon such as dichloromethane at a temperature from around ambient to the reflux temperature.

In another example, compounds containing a —L¹H or —L²H or group as defined above may be functionalised by acylation or thioacylation, for example by reaction with one of the alkylating agents just described but in which X¹ is replaced by a —C(O)X², C(S)X², —N(R⁸)COX² or —N(R⁸)C(S)X² group in which X² is a leaving atom or group as described for X¹. The reaction may be performed in the presence of a base, such as a hydride, e.g. sodium hydride or an amine, e.g. triethylamine or N-methylmorpholine, in a solvent such as a halogenated hydrocarbon, e.g. dichloromethane or carbon tetrachloride or an amide, e.g. dimethylformamide, at for example ambient temperature. Alternatively, the acylation may be carried out under the same conditions with an acid (for example one of the alkylating agents described above in which X¹ is replaced by a —CO₂H group) in the presence of a condensing agent, for example a diimide such as 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide or N,N′-dicyclohexylcarbodiimide, advantageously in the presence of a catalyst such as a N-hydroxy compound e.g. a N-hydroxytriazole such as 1-hydroxybenzotriazole. Alternatively the acid may be reacted with a chloroformate, for example ethylchloroformate, prior to the desired acylation reaction.

In a further example compounds may be obtained by sulphonylation of a compound containing an —OH group by reaction with one of the above alkylating agents but in which X¹ is replaced by a —S(O)Hal or —SO₂Hal group [in which Hal is a halogen atom such as chlorine atom] in the presence of a base, for example an inorganic base such as sodium hydride in a solvent such as an amide, e.g. a substituted amide such as dimethylformamide at for example ambient temperature.

In another example, compounds containing a —L¹H or —L²H group as defined above may be coupled with one of the alkylation agents just described but in which X¹ is replaced by an —OH group in a solvent such as tetrahydrofuran in the presence of a phosphine, e.g. triphenylphosphine and an activator such as diethyl, -diisopropyl- or dimethylazodicarboxylate.

In a further example, ester groups —CO₂R⁵, —CO₂Alk³ or —CO₂Alk⁷ in the compounds may be converted to the corresponding acid [—CO₂H] by acid- or base-catalysed hydrolysis depending on the nature of the groups R⁵, Alk³ or Alk⁷. Acid- or base-catalysed hydrolysis may be achieved for example by treatment with an organic or inorganic acid, e.g. trifluoroacetic acid in an aqueous solvent or a mineral acid such as hydrochloric acid in a solvent such as dioxan or an alkali metal hydroxide, e.g. lithium hydroxide in an aqueous alcohol, e.g. aqueous methanol.

In a further example, —OR⁵ or —OR¹⁴ groups [where R⁵ or R¹⁴ each represents an alkyl group such as methyl group] in compounds of formula (1) may be cleaved to the corresponding alcohol —OH by reaction with boron tribromide in a solvent such as a halogenated hydrocarbon, e.g. dichloromethane at a low temperature, e.g. around −78° C.

Alcohol [—OH] groups may also be obtained by hydrogenation of a corresponding —OCH₂R¹⁴ group (where R¹⁴ is an aryl group) using a metal catalyst, for example palladium on a support such as carbon in a solvent such as ethanol in the presence of ammonium formate, cyclohexadiene or hydrogen, from around ambient to the reflux temperature. In another example, —OH groups may be generated from the corresponding ester [CO₂Alk⁵ or CO₂R⁵] or aldehyde [—CHO] by reduction, using for example a complex metal hydride such as lithium aluminium hydride or sodium borohydride in a solvent such as methanol.

In another example, alcohol —OH groups in the compounds may be converted to a corresponding —OR⁵ or —OR¹⁴ group by coupling with a reagent R⁵OH or R¹⁴OH in a solvent such as tetrahydrofuran in the presence of a phosphine, e.g. triphenylphosphine and an activator such as diethyl-, diisopropyl-, or dimethylazodicarboxylate.

Aminosulphonylamino [—NHSO₂NHR²] groups in the compounds may be obtained, in another example, by reaction of a corresponding amine [—NH₂] with a sulphamide R²NHSO₂NH₂ in the presence of an organic base such as pyridine at an elevated temperature, e.g. the reflux temperature.

In another example compounds containing a —NHCSR² or —CSNHR² group may be prepared by treating a corrsponding compound containing a —NHCOR² or —CONHR² group with a thiation reagent, such as Lawesson's Reagent, in an anhydrous solvent, for example a cyclic ether such as tetrahydrofuran, at an elevated temperature such as the reflux temperature.

In a further example amine (—NH₂) groups may be alkylated using a reductive alkylation process employing an aldehyde and a borohydride, for example sodium triacetoxyborohyride or sodium cyanoborohydride, in a solvent such as a halogenated hydrocarbon, e.g. dichloromethane, a ketone such as acetone, or an alcohol, e.g. ethanol, where necessary in the presence of an acid such as acetic acid at around ambient temperature.

In a further example, amine [—NH₂] groups in compounds of formula (1) may be obtained by hydrolysis from a corresponding imide by reaction with hydrazine in a solvent such as an alcohol, e.g. ethanol at ambient temperature.

In another example, a nitro [—NO₂] group may be reduced to an amine [—NH₂], for example by catalytic hydrogenation using for example hydrogen in the presence of a metal catalyst, for example palladium on a support such as carbon in a solvent such as an ether, e.g. tetrahydrofuran or an alcohol e.g. methanol, or by chemical reduction using for example a metal, e.g. tin or iron, in the presence of an acid such as hydrochloric acid.

Aromatic halogen substituents in the compounds may be subjected to halogen-metal exchange with a base, for example a lithium base such as n-butyl or t-butyl lithium, optionally at a low temperature, e.g. around −78° C., in a solvent such as tetrahydrofuran and then quenched with an electrophile to introduce a desired substituent. Thus, for example, a formyl group may be introduced by using dimethylformamide as the electrophile; a thiomethyl group may be introduced by using dimethyldisulphide as the electrophile.

In another example, sulphur atoms in the compounds, for example when present in a linker group L¹ or L² may be oxidised to the corresponding sulphoxide or sulphone using an oxidising agent such as a peroxy acid, e.g. 3-chloroperoxybenzoic acid, in an inert solvent such as a halogenated hydrocarbon, e.g. dichloromethane, at around ambient temperature.

N-oxides of compounds of formula (1) may be prepared for example by oxidation of the corresponding nitrogen base using an oxidising agent such as hydrogen peroxide in the presence of an acid such as acetic acid, at an elevated temperature, for example around 70° C. to 80° C., or alternatively by reaction with a peracid such as peracetic acid in a solvent, e.g. dichloromethane, at ambient temperature.

Salts of compounds of formula (1) may be prepared by reaction of a compound of formula (1) with an appropriate base in a suitable solvent or mixture of solvents e.g. an organic solvent such as an ether e.g. diethylether, or an alcohol, e.g. ethanol using conventional procedures.

Where it is desired to obtain a particular enantiomer of a compound of formula (1) this may be produced from a corresponding mixture of enantiomers using any suitable conventional procedure for resolving enantiomers.

Thus for example diastereomeric derivatives, e.g. salts, may be produced by reaction of a mixture of enantiomers of formula (1) e.g. a racemate, and an appropriate chiral compound, e.g. a chiral base. The diastereomers may then be separated by any convenient means, for example by crystallisation and the desired enantiomer recovered, e.g. by treatment with an acid in the instance where the diastereomer is a salt.

In another resolution process a racemate of formula (1) may be separated using chiral High Performance Liquid Chromatography. Alternatively, if desired a particular enantiomer may be obtained by using an appropriate chiral intermediate in one of the processes described above.

Chromatography, recrystallisation and other conventional separation procedures may also be used with intermediates or final products where it is desired to obtain a particular geometric isomer of the invention.

The following Examples illustrate the invention. All temperatures are in ° C. The following abbreviations are used:

NMM - N-methylmorpholine; EtOAc - ethyl acetate; MeOH - methanol; BOC - butoxycarbonyl; DCM - dichloromethane AcOH - acetic acid; DIPEA - diisopropylethylamine; EtOH - ethanol; Pyr - pyridine; Ar - aryl; DMSO - dimethylsulphoxide; iPr - isopropyl; Et₂O - diethylether; Me - methyl; THF - tetrahydrofuran, DMF - N,N-dimethylformamide; FMOC - 9-fluorenylmethoxycarbonyl; TFA - trifluoroactic acid; All NMR's were obtained at 300 mHz.

Intermediate 1

s-Chloro-N-methylbenzimidazole

2-Chlorobenzimidazole (5.0 g, 32.7 mmol) was added to an ice cold suspension of sodium hydride (1.44 g, 36.0 mmol, 60% suspension in oil) in DMF (50 ml). After 30 min methyl iodide (2.14 ml, 34.3 mmol) was added and the mxiture stirred at 0° for a further 1 h. Water was then added and the product extracted into DCM, dried and evaporated to give the product as a brown solid (4.6 g, 85%). δH (CDCl₃) 7.70 (1H, m), 7.28 (3H, m), and 3.79 (3H, s). m/z (ES⁺, 70V) 167.5 (MH⁺).

Intermediate 2

Ethyl S-2-amino-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoate trifluoroacetate salt

N-t-butoxycarbonyl-p-amino-L-phenylalanine ethylester (2.0 g, 6.53 mmol) and Intermediate 1 (1.2 g, 7.19 mmol) were dissolved in ethoxyethanol (3 ml) and heated to 100° for 3 h. The reaction mixture was cooled and reduced to dryness in vacuo. The residue was dissolved in DCM (5 ml) and TFA (2.5 ml) added and the solution stirred for 2 h at room temperature. The volatiles were removed in vacuo and the residue azeotroped with heptane. The sticky residue was triturated with diethyl ether to give a solid precipitate which was collected and dried to give the title compound (1.5 g, 51%) δH (DMSO-d⁶) 7.59 (1H, d, J 7.2 Hz), 7.47 (2H, d, J 8.3 Hz), 7.40-7.22 (5H, m), 4.30 (1H, m), 4.14 (2H, q, J 7.0 Hz), 3.77 (3H, s), 3.17 (1H, dd, J 14.0, 6.0 Hz), 3.06 (1H, dd, J 14.0 and 7.8 Hz) and 1.14 (3H, t, J 7.0 Hz). m/z (ES⁺, 70V) 339 (MH⁺).

Intermediate 3

Ethyl S-2-{[2-(isopropoxy)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoate

Intermediate 2 (1.50 g, 3.32 mmol), diisopropylsquarate (0.72 g, 3.65 mmol) and DIPEA (0.87 ml, 4.98 mmol) were added to isopropanol (20 ml) and heated to 60° for 6 h. The mixture was then cooled and the volatiles removed in vacuo. Purification by flash chromatography (silica; 3:2 DCM/EtOAc) gave the title compound as an off white foam (1.3 g), δH (MeOD) 7.45 (1H, m), 7.34 (1H, m), 7.22 (3H, m), 7.10 (2H, m), 5.30 (1H, m), 5.15-4.60 (1H, v br.m), 4.24 (2H, q, J 7.0 Hz), 3.67 (3H, s), 3.30 (1H, m), 2.96 (1H, dd, J 14.0, 10.4 Hz), 1.40 (6H, m) and 1.29 (3H, t, J 7.0 Hz). m/z (ES⁺, 70V) 477 (MH⁺).

Intermediate 4

Methyl (S)-3-[4-{(thiophen[2,3-d]pyromidin-4-yl)amino}phenyl]-2-(t-butoxycaronylamino)propanoat

A solution of methyl (S)-3-[4-(aminophenyl)-2-(t-butoxycarbonylamino) propanoate (1.01 g, 3.6 mmol), 4-chlorothiophen[2,3-d]pyrimidine (0.61 g, 3.6 mmol) and DIPEA (0.69 ml, 4.0 mmol) in ethoxyethanol (0.8 ml) was heated to 120° under nitrogen for 5 h, then cooled to room temperature. The reaction mixture was dissolved in EtOAc, washed with water, dried (MgSO₄) and then concentrated in vacuo. The residue was purified by chromatography (silica; EtOAc/hexane, gradient elution 30-40%) to give the title compound (1.07 g, 72%). δH (CDCl₃) 8.61 (1H,s ), 7.59 (2H, d, J 8.4 Hz), 7.35 (1H, d, J 6.0 Hz), 7.14 (4H, m), 5.02 (1H, m), 4.58 (1H, m), 3.73 (3H, s), 3.10 (2H, m), 1.43 (9H, s). m/z (ES⁺, 70V) 429 (MH⁺).

EXAMPLE 1

Methyl S-2-{[2-(dipropylamino)-3,4-dioxo-1-cyclobutenyl]amino}-3-[4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoate

Intermediate 3 (430 mg, 0.91 mmol) was dissolved in MeOH (20 ml) and treated with dipropylamine (187 μl, 1.37 mmol) and heated to 60° overnight. The reaction was cooled and the volatiles removed in vacuo. The residue was purified by flash chromatography (silica; 3:2 DCM/EtOAc) to give the title compound as a white foam (250 mg). δH (MeOD) 7.44 (2H, d, J 8.5 Hz), 7.36 (1H, m), 7.24 (1H, m), 7.20 (2H, d, J 8.5 Hz), 7.10 (2H, m), 5.33 (1H, dd, J 10.3, 4.7 Hz), 3.79 (3H, s), 3.66 (3H, s), 3.49 (4H, br m), 3.35 (1H, dd, J 14.1, 4.7 Hz), 3.03 (1H, dd, J 14.1, 10.3 Hz), 1.59 (4H, m) and 0.88 (6H, t, J 7.3 Hz); m/z (ES⁺, 70V) 504 (MH⁺).

The compounds of Examples 2 and 3 were made in a similar manner to Example 1 using the amine indiciated.

EXAMPLE 2

Methyl S-2-{[2-(2,5-dimethylpyrrolidin-1-yl)-3,4-dioxo-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoate

Intermediate 3 treated with 2,5-dimethylpyrrolidine yielded the title compound (310 mg). δH (MeOD) 7.50-7.20 (8H, m), 5.36 (1H, m), 4.22 (2H, m), 3.81 (3H, s), 3.76 (3H, s), 3.43 (1H, m), 3.09 (1H, dd, J 13.6, 10.7 Hz), 2.20 (2H, m), 1.75 (2H, m), 1.34 (3H, d, J 6.5 Hz) and 1.30 (3H, d, J 6.5 Hz); m/z (ES⁺, 70V) 502 (MH⁺).

EXAMPLE 3

Methyl S-2-{[2-(2-methylpiperidin-1-yl)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidozol-2-yl)amino]phenyl}propanoate

Intermediate 3 treated with 2-methylpiperidine yielded the title compound (200 mg) δH (MeOD) 7.45 (2H, d, J 8.2 Hz), 7.36 (1H, m), 7.22 (3H, m), 7.09 (2H, m), 5.34 (1H, m), 4.46 (1H, m), 3.79 (3H, s), 3.66 (3H, s), 3.33 (1H, m), 3.00 (1H, m), 1.9-1.5 (8H, m) and 1.29 (3H, d, J 6.9 Hz); m/z (ES⁺, 70V) 502 (MH⁺).

EXAMPLE 4

S-2-{(2-Dipropylamino)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid

The compound of Example 1 (250 mg, 0.50 mmol) was dissolved in THF (5 ml) and water (5 ml) and lithium hydroxide monohydrate (25 mg, 0.55 mmol) added. The mixture was stirred at room temperature overnight. The THF was removed in vacuo and the remaining aqueous solution acidified to ˜pH 6 with 1 M HCl. The product was extracted into DCM, the organic layer dried (Na₂SO₄) and evaporated. Purification by flash chromatography (silica; 10% MeOH in DCM) gave the title compound as a white solid (207 mg). δH (DMSO-d⁶, 350K) 7.74 (2H, d, J 8.5 Hz), 7.39 (1H, m), 7.28 (1H, m,) 7.21 (2H, q, J 8.5 Hz), 7.08 (2H, m), 5.09 (1H, m), 3.46 (4H, m), 3.26 (1H, dd, J 14.0, 4.8 Hz), 3.09 (1H, dd, J 14.0, 9.3 Hz), 1.58 (4H, m) and 0.89 (6H, t, J 7.4 Hz); m/z (ES⁺, 70V) 490 (MH⁺).

Examples 5 and 6 were made in a similar fashion to Example 4

EXAMPLE 5

S-2-{(2-Dipropylamino)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid

Using the compound of Example 2 yielded the title compound (146 mg) δH (DMSO-d⁶, 350K) 7.60 (2H, d, J 8.6 Hz), 7.42 (1H, m), 7.31 (1H, m), 7.25 (2H, d, J 8.6 Hz), 7.11 (3H, m), 5.08 (1H, m), 4.40 (0.36H, (trans isomer) m), 4.28 (1.64H, (cis isomer), m), 3.74 (3H, s), 3.28 (1H, dd, J 14.1, 4.8 Hz), 3.14 (1H, dd, J 14.1, 8.9 Hz), 2.17 (2H, m), 1.76 (1.64H (cis isomer), m), 1.62 (0.36H, (trans isomer), m), 1.34 (2.45H, (cis isomer), d, J 6.4 Hz), 1.30 (2.45H (cis isomer), d, J 6.4 Hz), 1.17 (0.55H, (trans isomer), d, J 6.5 Hz) and 1.10 (0.55H, (trans isomer), d, J6.5 Hz); m/z (ES⁺, 70V) 488 (MH⁺).

EXAMPLE 6

S-2-{[2-(2-Methylpiperidin-1-yl)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid

Using the compound of Example 3 yielded the title compound (183 mg) δH (DMSO-d⁶, 350K) 7.70 (2H, d, J 8.5 Hz), 7.55 (1H, m), 7.45 (2H, m), 7.31 (2H, d, J 8.5 Hz), 7.20 (2H, m), 5.22 (1H, m), 4.53 (1H, m), 4.11 (1H, m), 3.78 (3H, s), 3.30-3.15 (2H, m), 1.90-1.50 (8H, m) and 1.30 (3H, t, J 6.8 Hz). m/z (ES⁺, 70V) 488 (MH⁺).

EXAMPLE 7

Methyl (S)-3-[4-{(thiophen[2,3-d]pyrimidin-4-yl)amino}phenyl]-2-[(isopropoxy-3,4-dioxocyclobut-1-enyl)amino]propanoate

A solution of Intermediate 4 (1.07 g, 2.5 mmol) was stirred with a EtOAc solution of HCl (2.6M, 10 ml) for 1.5 h. The mixture was diluted with EtOAc (75 ml) and NaHCO₃ solution added. The organic layer was separated, washed with brine, dried (MgSO₄) and concentrated in vacuo. The crude proudct was dissoled in EtOH and 3,4-diisopropoxy-3-cyclobutene-1,2-dione (0.49 g, 2.5 mmol) and 3,4-diisopropoxy-3-cyclobutene-1,2-dione (0.49 g, 2.5 mmol) and DIPEA (0.46 g, 3.8 mmol) added. The reaction was stirred for 16 h then concentrated in vacuo, the residue dissolved in EtOAc, washed with 10% citric acid, NaHCO₃ solution and brine, dried (MgSO₄) and concentrated in vacuo. The residue was purified by chromatography (silica; DCM/MeOH 95:5) to give the title compound as a pale yellow solid (0.91 g, 60%). δH (CDCl₃) 8.60 (1H, s), 7.62 (2H, d, J 8.5 Hz), 7.38 (1H, d, J 6.0 Hz), 7.24-7.13 (4H, m), 5.34 (1H, m), 3.82 (3H, s), 3.22 (2H, m), 1.41 (3H, d, J 6.1 Hz), 1.39 (3H, d, J 6.1 Hz); m/z (ES⁺, 70V) 467 (MH⁺).

EXAMPLE 8

Ethyl-(S)-3-[4-(thiophen[2,3-d]pyrimidin-4-ylamino)phenyl]-2-(2-diethylamino-3,4-dioxocyclobut-1-enylamino)propanoate

A solution of the compound of Example 7 (0.50 g, 0.11 mmol) in EtOH (8 ml) was treated with diethylamine (0.22 ml, 0.22 mmol) and stirred at 45° for 16 h. The reaction was concentrated in vacuo, the residue dissolved in EtOAc, washed with brine, dried (MgSO₄) and concentrated in vacuo. The residue was purified by chromatography (SiO₂; DCM/MeOH 9:1) to give the title compound as a yellow foam (0.46 g, 89%). δ_(H) (CDCl₃) 8.58 (1H, s), 7.64 (2H, d, J 8.5 Hz), 7.42 (1H, s), 7.36 (1H, d, J 5.95 Hz), 7.28 (2H, n r m), 7.15 (2H, d, J 8.51 Hz), 5.38 (1H, br s), 4.24 (2H, dd, J 14.3, 7.17 Hz), 3.62-3.35 (2H, m), 3.3-3.1 (2H, m), 1.30 (3H, t, J 7.18 Hz), 1.26-1.20 (6H, m). m/z (ES⁺, 70V) 494 (MH⁺).

EXAMPLE 9

(S)-3-[4-(Thiophen[2,3-d]pyrimidin-4-ylamino)phenyl]2-(2-(diethylamino-3,4-dioxocyclobut-1-enylamino)propanoic acid

A solution of the compound of Example 8 (0.45 g, 0.09 mmol) in dioxan (2 ml), MeOH (1 ml) and water (2 ml) was treated with LiOH.H₂O (58 mg, 1.35 mmol) and the reaction sitrred for 5 h, acidified with AcOH and concentrated in vacuo. The residue was purified by chromatography (SiO₂; DCM/MeOH/AcOH/H₂O 200/20/3/1) to give the title compound as a white solid (0.31 g, 68%). δH (DMSO, 390K) 8.52 (1H, s), 7.82 (1H, d, J 6.0 Hz), 7.77 (2H, d, J 8.5 Hz), 7.65 (1H, d, J 6.0 Hz), 7.33 (2H, d, J 8.7 Hz), 5.22 (1H, br s), 3.67-3.57 (4H, m), 3.35 (1H, dd, J 14.2, 5.1 Hz), 3.18 (1H, dd, J 14.2, 9.1 Hz), 1.22 (6H, t, J 7.1 Hz); m/z (ES⁺, 70V) 466 (MH⁺).

The following assays can be used to demonstrate the potency and selectivity of the compounds according to the invention. In each of these assays an IC₅₀ value was determined for each test compound and represents the concentration of compound necessary to achieve 50% inhibition of cell adhesion where 100%=adhesion assessed in the absence of the test compound and 0%=absorbance in wells that did not receive cells.

α₄β₁ Integrin-dependent Jurkat Cell Adhesion to VCAM-Ig

96 well NUNC plates were coated with F(ab)₂ fragment goat anti-human IgG Fcγ-specific antibody [Jackson 1 mmuno Research 109-006-098: 100 μl at 2 μg/ml in 0.1M NaHCO₃, pH 8.4], overnight at 40. The plates were washed (3×) in phosphate-buffered saline (PBS) and then blocked for 1 h in PBS/1% BSA at room temperature on a rocking platform. After washing (3× in PBS) 9 ng/ml of purified 2d VCAM-Ig diluted in PBS/1% BSA was added and the plates left for 60 minutes at room temperature on a rocking platform. The plates were washed (3× in PBS) and the assay then performed at 37° for 30 min in a total volume of 200 μl containing 2.5×10⁵ Jurkat cells in the presence or absence of titrated test compounds.

Each plate was washed (2×) with medium and the adherent cells were fixed with 100 μl MeOH for 10 minutes followed by another wash. 100 μl 0.25% Rose Bengal (Sigma R4507) in PBS was added for 5 minutes at room temperature and the plates washed (3×) in PBS. 100 μl 50% (v/v) ethanol in PBS was added and the plates left for 60 min after which the absorbance (570 nm) was measured.

α₄β₇ Integrin-dependent JY Cell Adhesion to MAdCAM-Ig

This assay was performed in the same manner as the α₄β₁ assay except that MAdCAM-Ig (150 ng/ml) was used in place of 2d VCAM-Ig and a sub-line of the β-lympho blastoid cell-line JY was used in place of Jurkat cells. The IC₅₀ value for each test compound was determined as described in the α₄β₁ integrin assay.

α₅β₁ Integrin-dependent K562 Cell Adhesion to Fibronectin

96 well tissue culture plates were coated with human plasma fibronectin (Sigma F0895) at 5 μg/ml in phosphate-buffered saline (PBS) for 2 hr at 37° C. The plates were washed (3× in PBS) and then blocked for 1 h in 100 μl PBS/1% BSA at room temperature on a rocking platform. The blocked plates were washed (3× in PBS) and the assay then performed at 37° C. in a total volume of 200 μl containing 2.5×10⁵ K562 cells, phorbol-12-myristate-13-acetate at 10 ng/ml, and in the presence or absence of titrated test compounds. Incubation time was 30 minutes. Each plate was fixed and stained as described in the α₄β₁ assay above.

α_(m)β₂-Dependent Human Polymorphonuclear Neutrophils Adhesion to Plastic

96 well tissue culture plates were coated with RPMI 1640/10% FCS for 2 h at 37° C. 2×10⁵ freshly isolated human venous polymorphonuclear neutrophils (PMN) were added to the wells in a total volume of 200 μl in the presence of long/ml phorbol-12-myristate-13-acetate, and in the presence or absence of test compounds, and incubated for 20 m in at 37° C. followed by 30 min at room temperature. The plates were washed in medium and 100 μl 0.1% (w/v) HMB (hexadecyl trimethyl ammonium bromide, Sigma H5882) in 0.05M potassium phosphate buffer, pH 6.0 added to each well. The plates were then left on a rocker at room temperature for 60 min. Endogenous peroxidase activity was then assessed using tetramethyl benzidine (TMB) as follows: PMN lysate samples mixed with 0.22% H₂O₂ (Sigma) and 50 μg/ml TMB (Boehringer Mannheim) in 0.1M sodium acetate/citrate buffer, pH 6.0 and absorbance measured at 630 nm.

αIIb/β₃-Dependent Human Platelet Aggregation

Human platelet aggregation was assessed using impedance aggregation on the Chronolog Whole Blood Lumiaggregometer. Human platelet-rich plasma (PRP) was obtained by spinning fresh human venous blood anticoagulated with 0.38% (v/v) tri-sodium citrate at 220× g for 10 min and diluted to a cell density of 6×10⁸/ml in autologous plasma. Cuvettes contained equal volumes of PRP and filtered Tyrode's buffer (g/liter: NaCl 8.0; MgCl₂.H₂O 0.427; CaCl₂ 0.2; KCl 0.2; D-glucose 1.0; NaHCO₃ 1.0; NaHPO₄.2H₂O 0.065). Aggregation was monitored following addition of 2.5 μM ADP (Sigma) in the presence or absence of inhibitors.

In the above assays the preferred compounds of the invention in which R¹ is an α4 integrin binding group, such as the compounds of the Examples generally have IC₅₀ values in the α₄β₁ and α₄β₇ assays of 1 μM and below. In the other assays featuring α integrins of other subgroups the same compounds had IC₅₀ values of 50 μM and above thus demonstrating the potency and selectivity of their action against α₄ integrins.

The advantageous clearance properties of compounds according to the invention may be demonstrated as follows:

Hepatic clearance, whether metabolic or biliary, can make a substantial contribution to the total plasma clearance of a drug. The total plasma clearance is a principal parameter of the pharmacokinetic properties of a medicine. It has a direct impact on the dose required to achieve effective plama concentrations and has a major impact on the elimination half-life and therefore the dose-interval. Furthermore, high hepatic clearance is an indicator of high first-pass hepatic clearance after oral administration and therefore low oral bioavailability.

Many peptidic and non-peptidic carboxylic acids of therapeutic interest are subject to high hepatic clearance from plasma. Except for drugs which function in the liver, hepatic uptake from blood or plasma is undesirable because it leads to high hepatic clearance if the compound is excreted in bile or metabolised, or if the substance is not cleared from the liver, it may accumulate in the liver and interfere with the normal function of the liver.

The total plasma clearance of a compound according to the invention can be determined as follows:

a small dose of the compound in solution is injected into a vein of a test animal. Blood samples are withdrawn from a blood vessel of the animal at several times after the injection, and the concentration of compound in the bleed or plasma is measured using a suitable assay. The area under the curve (AUCiv) is calculated by non-compartmental methods (for example, the trapezium method) or by pharmacokinetic modelling. The total plasma clearance (CL_(p)) is calculated by dividing the intravenous dose(D_(iv)) by the AUC_(iv) for the blood plasma concentration−time course of a drug administered by the intravenous route: CL_(p)=D_(iv)÷AUC_(iv)

When tested in this manner, compounds according to the invention are not rapidly or extensively extracted by the liver and have low total plasma clearance where low is defined as less than 10 ml/min/kg in the laboratory rat (Sprague Dawley CD). This compares favourably with functionally equivalent integrin binding compounds in which the squaric acid framework of compounds of formula (1) is not present. 

We claim:
 1. A compound of formula (1):

wherein Het is a bicyclic fused ring heteroaromatic group; g is zero or the integer 1, 2, 3 or 4; Each R¹⁶, which may be the same or different, is an atom or group —L³(Alk²)_(t)L⁴(R⁴)_(u), L³ and L⁴, which may be the same or different, are each a covalent bond or a linker atom or group —O—, —S—, —C(O)—, —C(O)O—, —OC(O)—, —C(S)—, —S(O)—, —S(O)₂—, —N(R⁸)—, —N(R⁸)O—, —N(R⁸)N—, —CON(R)⁸)—, —OC(O)N(R⁸)—, —CSN(R⁸)—, —N(R⁸)CO—, —N(R⁸)C(O)O—, —N(R⁸)CS—, —S(O)₂N(R⁸)—, —N(R⁸)S(O)₂—, —N(R⁸)CON(R⁸)—, —N(R⁸)CSN(R⁸)—, or —N(R⁸)SO₂N(R⁸)—, R⁸ is a hydrogen atom or an optionally substituted C₁₋₆alkyl group, t is zero or the integer 1, u is an integer 1, 2 or 3, Alk² is an aliphatic or heteroaliphatic chain, and R⁴ is a hydrogen or halogen atom or a group selected from an optionally substituted C₁₋₆alkyl or C₃₋₈ cycloalkyl group, —OR⁵ (where R⁵ is a hydrogen atom, an optionally substituted C₁₋₆alkyl or C₃₋₈ cycloalkyl group), —SR⁵, —NR⁵R⁶ (where R⁶ is as just defined for R⁵ and may be the same or different), —NO₂, —CN, —CO₂R⁵, —SO₃H, —SOR⁵, SO₂R⁵, —SO₃R⁵, —OCO₂R⁵, —CONR⁵R⁶, —OCONR⁵R⁶, —CSNR⁵R⁶, —COR⁵, —OCOR⁵, —N(R⁵)COR⁶, —N(R⁵)CSR⁶, —SO₂N(R⁵)(R⁶), —N(R⁵)SO₂R⁶, —N(R⁵)CON(R⁶)(R⁷), (where R⁷ is a hydrogen atom, an optionally substituted C₁₋₆alkyl or C₃₋₈cycloalkyl group), —N(R⁵)CSN(R⁶)(R⁷) or —N(R⁵)SO₂N(R⁶)(R⁷), provided that when t is zero and each of L³ and L⁴ is a covalent bond then u is the integer 1 and R⁴ is other than a hydrogen atom; L² is a covalent bond or an atom or group —O—, —S—, —C(O)—, —C(S)—, —S(O)—, —S(O)₂, —N(R⁸)— or —C(R⁸)(R^(8a))— (where R^(8a) is an atom or group as defined for R⁸ and may be the same or different); Ar² is an optionally substituted aromatic or heteroaromatic group; Alk is a chain

in which R is a carboxylic acid (—CO₂H), a carboxylic acid ester, a carboxylic acid amide, or a carboxylic acid biostere; R¹ is a hydrogen atom or a C₁₋₆alkyl group; L¹ is a covalent bond or a linker atom or group —O—, —S—, —C(O)—, —C(O)O—, —OC(O)—, —C(S)—, —S(O)—, —S(O)₂—, —N(R⁸)—, —N(R⁸)O—, —N(R⁸)N—, —CON(R⁸)—, —OC(O)N(R⁸)—, —CSN(R⁸)—, —N(R⁸)CO—, —N(R⁸)C(O)O—, —N(R⁸)CS—, —S(O)₂N(R⁸)—, —N(R⁸)S(O)₂—, —N(R⁸)CON(R⁸)—, —N(R⁸)CSN(R⁸)—, or —N(R⁸)SO₂N(R⁸)—; Alk¹ is an optionally substituted aliphatic chain; n is zero or the integer 1; R² is a hydrogen atom or an optionally substituted heteroaliphatic, C₃₋₁₀cycloaliphatic, C₃₋₁₀heterocycloaliphatic, C₇₋₁₀polycycloaliphatic, C₇₋₁₀heteropolycycloaliphatic, aromatic or heteroaromatic group, wherein said heteroaliphatic, C₃₋₁₀heterocycloaliphatic, and C₇₋₁₀heteropolycycloaliphatic groups contain one, two, three, or four heteroatoms or heteroatom-containing groups as defined for L³ and L⁴, which may be the same or different; provided that Het is not a 2,6-naphthyridin-1-yl, isoquinolin-1-yl, 2,7-naphthyridin-1-yl or quinazolin-4-yl group; and the salts and N-oxides thereof.
 2. A compound according to claim 1 in which Alk is a chain


3. A compound according to claim 1 in which R is a carboxylic acid (—CO₂H) group.
 4. A compound according to claim 1 in which R is an esterified carboxyl group of formula —CO₂Alk⁷.
 5. A compound according to claim 1 in which R¹ is a hydrogen atom.
 6. A compound according to claim 1 in which Ar² is an optionally substituted phenylene group.
 7. A compound according to claim 1 in which L¹ is a —N(R⁸)— group where R⁸ is a hydrogen atom or an optionally substituted C₁₋₆alkyl group.
 8. A compound according to claim 7 in which R⁸ is a methyl, ethyl or n-propyl group.
 9. A compound according to claim 1 in which L¹ is a covalent bond.
 10. A compound according to claim 1 in which n is the integer 1, Alk¹ is an optionally substituted straight or branched C₁₋₆alkylene chain and R² is a hydrogen atom.
 11. A compound according to claim 10 in which Alk¹ is a —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂— or —C(CH₃)₂CH₂— chain.
 12. A compound according to claim 1 in which L¹ is a covalent bond, n is zero and R² is an optionally substituted C₅₋₇heterocycloaliphatic group.
 13. A compound according to claim 12 in which R² is an optionally substituted piperidinyl, homopiperidinyl, heptamethyleneiminyl, pyrrolidinyl, piperazinyl, homopiperazinyl, morpholinyl or thiomorpholinyl group.
 14. A compound according to claim 1 in which L² is an —O— atom or —N(R⁸)— group in which R⁸ is a hydrogen atom or an optionally substituted C₁₋₆alkyl group.
 15. A compound according to claim 1 of formula (2a):

wherein: R¹⁷ is an atom or group R¹⁶ as previously defined; h is zero or the integer 1, 2 or 3; R¹⁸ is a hydrogen atom or an atom or group R¹⁶ as previously defined; and the salts and N-oxides thereof.
 16. A compound according to claim 1 of formula (2b):

wherein: X, Y and Z is each independently selected from a nitrogen, oxygen or sulphur atom or CH group; the broken line ( - - - ) represents saturation or unsaturation; and the salts and N-oxides thereof.
 17. A compound according to claim 16 in which X is an O or S atom, Y and Z are each a group CH, a single bond joins X and Y and a double bond joins Y and Z.
 18. A compound according to claim 16 in which Z is an O or S atom, X and Y are each a CH group, a single bond joins Y and Z and a double bond joins X and Y.
 19. A compound which is: S-2-{[2-Dipropylamino)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid; S-2-{[2-Dipropylamino)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid; S-2-{[2-(2-Methylpiperidin-1-yl)-3,4-dioxo-1-cyclobutenyl]amino}-3-{4-[(1-methylbenzimidazol-2-yl)amino]phenyl}propanoic acid; (S)-3-[4-(Thiophen[2,3-d]pyrimidin-4-ylamino)phenyl]2-(2-(diethylamino-3,4-dioxocyclobut-1-enylamino)propanoic acid; and the salts, N-oxides and carboxylic acid esters thereof.
 20. A compound according to claim 19 wherein the carboxylic acid esters are selected from the group consisting of methyl, ethyl, propyl, and i-propyl.
 21. A pharmaceutical composition comprising a compound according to claim 1 together with one or more pharmaceutically acceptable carriers, excipients or diluents.
 22. A method for the treatment of inflammatory arthritis, allograft rejection, diabetes, inflammatory dermatoses, asthma or inflammatory bowel disease comprising administering to a mammal suffering from such a disease or disorder a therapeutically effective amount of a compound according to claim
 1. 23. A method according to claim 22 wherein said inflammatory arthritis is selected from the group consisting of rheumatoid arthritis, vasculitis and polydermatomyositis.
 24. A method according to claim 22 wherein said inflammatory dermatoses are selected from the group consisting of psoriasis and dermatitis. 